Most of these are foam / brown paper http://www.aircombat.bezstarosti.cz/...ly/fotomod.htm

Just get some brown wrapping paper, cut to shape slightly coversize, apply pva thinned about 50% with water to the dull side leave a couple of minutes and apply to foam and leave to dry. If it was a wing do not panic when you go to do the other side, yes it will be badly bowed but it will flatten out when you do the other side. That brown paper really shrinks. If there is still a bow or warp after you have covered both sides just brush on some water [ or very dilute pva ] and use a hair dryer or film heat gun to dry the side you want to shrink first. I apply a total of two coats 50/50 pva water then rub down with 400 grade. paint on a sealing layer of Flexcoat [ does not attack blue foam. ] then paint as required. As I fly combat I do not aim for a concours finsh but a concours finish is possible with a little extra sanding. The resultant stressed skin structure is surprisingly rigid. I can not remember ever seeing a wing fold in combat.

Here are some of mine.