So, here's the tip. If you use un-oiled steel wool to knock dust spots and such out of base color, be sure to really clean the surface before shoot catalyzed polyurethane clear coat. If not, it's not pretty.

specks of steel in the clear. Argh.......

otherwise known as really really light metallic flake,, muah hahaha,,

OK, I was feeling all virtuous for not making a joke out of Randy's tragedy.  Now I'm just regretting not being the first in with the knife.

So, Randy -- whassamata with metallic paint jobs?

I usually use steel wool sanding on open bays.  I run a magnet over the airplane and it picks up lots of steel fuzzies.

Mark,

Yes, the Avenger (just the cowl). Worst case, I'll sand it out and repaint. Sigh....

Wayne,

Steel wool (non-oiled) is really good for hitting curved areas, nooks and crannies and such. Harder to go through the clear. I use it on open bays, things like the cowl and other various areas. I use sandpaper on flat areas (with soft block behind). The idea is go cut the clear and flatten it. Then polish it up.

Usually, I just clean the surface (or part) with Windex ala Phil Granderson. Sometimes I use Prep-Sol or similar. I had used a bit of steel wool to knock down some dust I got in the base coat. I just flat forgot to clean it before I shot clear. Weirdly, I cleaned the plane and landing gear. go figure.

Steel wool (non-oiled) is really good for hitting curved areas, nooks and crannies and such. Harder to go through the clear.

Wayne, if you're still mystified, it's because sandpaper tends to try to make everything flat over a large dimension -- it just rides on whatever is the highest for an inch or two around (more if you back it with a block or board).  Since it grinds down what it's riding on and not what it isn't touching, that means it'll take off paint there whether you want it to or not.

When you're sanding, you select a sanding medium to match what you're sanding.  If you go into an auto paint shop you'll see sanding boards ranging from two feet long down to six inches, then you'll see rubber blocks that are around six inches long.  Boat shops may have boards that are longer yet.  The long boards (my dad called them "idiot boards") are used for sanding long panels that don't have much curvature, like the side of most cars from the mid-1950's on.  The rubber blocks would be used on something with moderate curvature, like the trunk lid of a 1940 Ford or similar car.  When you get down to fenders and bullets and reveals and such, you'll grab the sand paper in your bare hand and use that.

Steel wool just takes things one step further.  Assuming you've already achieved the shape you want, the steel wool will ride down into depressions, and follow the curve off of a wing rib into the covering next to it, etc.  It'll still grind down the high spots -- but it'll only be able to "see" high and low over a fraction of an inch, so it won't cut through the covering at the edges of your ribs, or sand all the paint off of some corner, the way sandpaper will want to do.