As you say, dope is versatile stuff. Clear dope can be used to stick down paper or fabric, to fill pores in wood, etc, etc. and to make a nice shiny surface. Use of colored dope is obvious. Nitrate sticks and fills very well, but is not fuelproof. Butyrate is fairly fuelproof, but takes a while to completely dry and will keep shrinking for a long time. Blushing can be stopped by adding retarder (Sig makes some). I once doped a wing with clear butyrate with retarder outside in a light rain with no problem. Shrinking can be reduced with a plasticizer. Sig litecoat is plasticized to some extent, as are the Sig colors.

Jim