Depending on what you are trying to accomplish, there's some highly toxic
, semi-toxic
, and many non-toxic
, products out there. Many aren't specifically made or marketed for the model airplane builder, and some you have to be really creative to think up. ALWAYS read the caution labels, and never take the position "I'll just hold my breath with I'm pouring the stuff with the MEK in it..." Some materials have good, others excellent strength characteristics. Depending whether your application is cosmetic or structural, whether a detail part can be cast, and whether you're talking about 1/72 or 1/3 scale, consider:
Bondo
auto filler putty
sandable auto primer
Gesso
Sculpey (see sculpey.com)
Great-Stuff (the expanable insulation foam that hardens)
POR-15
plaster and plaster first sifted through a piece
of cloth (this gives you a very fine detail finish) mixed with gesso that
can be poured in to a mold made of play-doh, clay, etc.
the broad range of products from smooth-on.com - this
company and their products are tremendous.
There's many more too, to experiment and discover is the key...