Sorry if this has been asked a zillion times before, but here goes:

I used Sig nitrate as the adhesion coat on an Olympic Mark VI covered with silkspan, then Sig clear butyrate as the filler coat, and now have on several coats of Brodak "white primer," kind of a light grey butyrate. Using Randolph butyrate thinner in all the butyrate products. Wet sanded the primer coats with 600 grit and have a nice smooth substrate for the white "base" or more properly "finish" coat. I am doing a replica of Gialdini's paint scheme, almost all white. I will be using Sig white dope followed by Randolph's non-tautening clear.

What is the concensus on sanding between coats of the white base/finish? And then, once the white has gassed off for a few weeks, what about sanding (I have 1500 and 2000 grit wet paper) the last white coat before the clear goes on? And finally, what about sanding the clear coats, including the final coat before buffing? I am not going for (nor capable of) a 20-point finish, but want it to look good. Without spending 300 hours on it.

Agreed with Randy,
One additional problem that can come from sanding base coats especially white, is that trace color elements can actually hide in the sanding scratches and when you shoot clear, they come back to haunt you in the way of color patches. ESPECIALLY with red or maroons. If you are going to sand on the color coats, I would NOT sand anything red or maroon, and only sand the white lightly to get rid of dirt nibs. You should be spraying the white evenly enough that sanding texture, or orange peal, is not a concern.
I would just touch the spots where you have dirt chunks lightly with 600 but be advised you may need to spray that area lightly again to cover the sanded off dirt spot or you will end up with a black fleck .
best solution, dont sand after you put your final color coats on, sand only on the clear. On Dope, I would sand with 1200 or 1500  prior to buffing. You can sand lightly to  open the surface up  and accelerate the "gassing" off of the clear coats. Then sand thouroughly prior to buffing. This of course after a LONG dry period.

Randy,
I agree with the theory, However I don't like the idea of sanding color with 1500. The finest I would recommend sanding color coats with is 800 or possibly 1200 and never, NEVER sand any color that has metallic or pearl in it ( or candy for that matter)
The problem I have with sanding that fine on color coats is , the tendency in our world is to put on light coats, with 1500 grit scratches, you don't gain any mechanical tooth . When you spray light layers with lacquer, you are depending upon mechanical tooth to hold the coat in place until you "flood" it with clear to melt it all together/ The particles of paint that hit the surface can actually bridge over the scratch and form non adhesive areas. I would much rather see a slightly larger scratch pattern to insure mechanical grip for subsequent layers. Bopttom line, unless you are spraying pearls, you wont see an 800 grit scratch. In fact, I prep sand with 400 dry a lot of times. The only advantage that I can see to using finer grits ( read that 1200 or 1500 ) is that you wont sand through the color.

Remember with lacquer, you must get solvent penetration in order to have good adhesion. However, this solvent penetration can come from later coats as the solvent will push all the way to the base and then back out if there is enough solvent, and enough time. This is why every coat you spray brings back those darn imperfections that you so carefully sanded away ( that is if you pound on the coats to fast or to heavy)

Mike, you've seen my planes. There is no sanding at all between the first color coat and the last of the trim colors (except for knocking down the ridge the trim tape leaves.) After primer sanding, I don't touch it again untill some clear is on it.

Thanks guys! If our nice weather holds I will be able to get the white "color" coats on in the next few days. The feeling seems to be either no sanding of color coats at all, or very minimal. I am glad to hear it since wet sanding is a gawdawful mess on my patio and usually in my shoes. There will be only a very little amount of red trim in keeping with Gialdini's paint scheme.

Randy,
One caution with Steel wool, a LOT of steel wool is treated with oil to prevent corrosion of the fine fibers. I think that some woodworking steel wool is oil free. Just another thing that can bite you if you are unsuspecting,, yeah go ahead, ask me how I know THIS one!  The credit card trick works well if the color is totally dry, something I have seen bite people is to try to "scrape" it before its dry enough, and it just folds back on itself and sticks!

I know you and lots of others know this stuff, but by my nature, I always assume somebody is reading that doesnt know, so I have to be nit picky, sorry if its boring to ya'all

did you say you were jetting off to the land of bikinis and sand sometime soon?

In my years of working with dope finishes I have had every one of the problems listed above happen to me. It is still a trial and error process but  at least now I know that I do not suffer alone. Thanks guys. 

SWEET, now if you were really with it, you would have AutoCad loaded in the laptop and you could design your next three stunters under the watchfull eye of the pacific sun