O.K.  Theory is its a ' flying machine ' you pays youre money and you makes your choices.

Plastic film finishes are probly a darn site easier , more fuel resistant , and S.F.A. differant
WEIGHT WISE. so wy do we bother .Must be habbit. Brought up on 50s & 60s Aeromuddler on the computor and copy them.On to paper , AS.
magazines. argh. That explains it.

Rightio , We're after the top performance and most effecient airframe.

We might ' score a few points ' structurally here , as the DOPE holds and bonds the wood
surfaces together , and hardens and stiffens them . AND ' we ' use Blsa Cement too . . . .

  Read somewhere that the ' Nitro celluloids ' in the stuff were chemically comparable
 to the ' celluloid ' structure molecularly , of ' Balsa Wood ' . So there ' like ' substances.

Someone can nodoubt further enlighten us on this astounding piece of information.

The problem ' overseas' these days is aircraft are no longer commonly made with linen & DOPE.
4 gallon cans of Aircraft Dope were $ 30 & thinner $ 20. Required thinning near 50 % initially so
about two thinners to one dope , on the budjet , the cement cme in the big cans too . . .

So were we go , if you havnt died of boredom yet.It was all very simple.Chewing dope of the fingers for days afterward.

After the airframes doped and sanded , 4 coats , sanding between Ea two,The Tissues applied,starting from the corner .Or an edge
but ordinarrily from something like the middle. So this is where all the skill comes in. getting it all flat and even and no stresses.
Usually its brushed down held taught, with thinners , to the prepared surface.Or maybe tinned dope.

Next is brushing on a few coats of thickish dope to fill the pores ! (big word) Ive tried spraying at this stage to save weight. Almost
 works as it doesnt go through as much.
The big bug bear is dope soaking through , getting on the edges of the cap strips , and elsewhere.The shrinking effect pulls it all
 anywhere its attached itself to, and put ' ghastly ' ridges all over the place.So we avoid this at all cost. Maybe dopeing the center
of the panels first, to shrink it all off, and warrily dopeing the bits over things only , next.With a nice soft brush , no pressure , and
SPAREINGLY fo a few coats.
Who said this was fun.On a fine day you do it outdoors , or leave all the windows open, have a fan . etc and so on. As the Stuff is TOXIC
These days. Tolulene , Zylene , and other nasties that DIDNT EXIST when DOPE was Nitro Cellulose Lacqure . LITERALLY . Natural Componds.

So to avoid brain damadge we have ' VENTILATION' please.

Once all this conundrum is done succesfully, we save more weight. WE DO ALL THE " GRAPHICS " in tissue . This actually looks really classy
as its TRANSLUCENT and displays ones magnificent building skills.If you dont look like you ' have a problem ' as youre still chewing dried dope
of youre fingers and you have a dazed distant outlook as you left it in your bedroom to ' gas off ' the fumes for the last fortnite.

' The ' GASSING OFF ' is the dissapation of the evaoratives. If one has the patiance of a saint , or other things to do . its Two Days between coats.
to stop sealing these in , and causing ' Problems '. as the thing takes ten weeks to harden up. or till next summer, or the one after.Nothing but fun . !

Traditionally a drop or two of ' castor oil ' was added to Ea Gallon, as a ' plasticiser ' ..To give some flexibility. so there wernt holes everywhere
( see ' paspallum ' )

SO , we've figured what astounding grapics to apply ? A soft HB or 2H ( prefered) pencil is used to apply guide marks , with a straigt edge.If your really keen youll use a 6H sharpened nicely. Droped nose down , they go straight throuh open bays. AND if the pencils doped over , you cant brush it of. So thats another
stage. Getting all the bits of coloured tissue possitioed and fastened with thinner , and if of light colours , getting the pencil lines ruubed of before dopeing the edges.
The Skinflint method involved getting Newspapers , Finding the desired ' script ' cutting all the letters out in oversize squares or strips( these days youd acess styles on this contraption and print them on A4 paper)
We get a new packet of Knife Blades FOR ALL TISSUE WORK,
throw some paper on a board , throw on six or so layers of the desired colour of tissue ,smooth it down , throw ( position carefully ) the script over, Smooth , and Pin Down.Then its the straight edge and scalple, doing centres before cutting things loose, they move then ! , and roundds free hand. This is all like ' Penmanship ' which was taught in primary school once.
Darn sight more accurate positionng a corner first , sticking em down. light thinner and a nice brush. Youve about two seconds to check alignment and lift if its off, or itll start to bond

So this about covers it.
Brushing in a few coats , light sanding with fine paper to feather the edges, and all the rest is a pleasure.If you havnt lost the plot from hemical inhalation.

Spaying the rests good value , but not nessesary if you have good brushes , and PATIANCE.
SUNSHINE is a fairly desireable ingrediant too.Humidity and dampness puts it all in the ' too hard ' basket, as the moisture is absorbed, it goes all ' milky ' and looks like a dogs breakfast, that came up again.

Really cunning aplication with the bare minimum of dope at all stages from bare wood, can get an open pored finish on all surfaces.

This way flash new two pot can be applied, sprayed, to bond for maximum toughness. Or if a raceing aircraft or fully sheeted , heated two pot trowled on and scred off with credit cards to leave the minimum requirement. This is Liable to be a complete dog to sand and never finish flat,so practise on scrap.AS THEY SAY 
No doubt youre al looking forward to try this . As they used to say in 'Old Blightey ' You dont have to be mad to be an aeromodellor , but it helps.

And remember the ventilation , with these new fangled substitutes for the real thing , the meanace is liable to be more permanant.

Perhaps just enjoying an adult beverage?   

One thing learned during 15 years of building and flying F1A's is that the first coat of clear is the one that adds most the weight. I do not recall how much that first coat added, but subsequent coats (on 230 sq. inches, half the two piece wing) was always in the tenths of a gram, and sometimes was not measurable with my Ohaus Tri-Beam balance (.1 gram graduation). This was always pretty well thinned nitrate, but I'm not convinced that nitrate would weigh less than butyrate, but didn't try to find out. I did use SIG Lite-Coat when it first came out, but later changed to Nitrate. It was fuel proof enough for gliders.

The conclusion I reached was that the coats #2 > 10 or 20 was pretty much penalty free, and the guy that figures out a way to reduce the weight gain of that #1 coat has really done himself some good. I think a very careful brushing with very highly thinned clear would be key. Intuition tells me that spraying a light and thin first coat oughta be lighter, but Joe Dill once told me that brushed finishes were lighter than sprayed. This tells me that either spray painters tend to spray too much material, or the brusher knows he has to sand more to get the brushmarks out, and either does that, or learns to avoid brushmarks. It therefore makes sense to build your finish with clear, and only use primer or filler where you really have to fix some problems. 

I don't know squat about pigmented dope, except that it's heavy, so using the least amount possible would have to be good.  Steve

I think the best tool for reducing weight on any model is "sandpaper" or glasspaper as I was constantly reminded during woodwork lessons at school

Cheers