for hardening wood like balsa i have tried minwax wood hardener and find it works pretty good,almost turns the wood into plastic and u can use various glues later with it,i make my wings out of balsa,rudder and elevator too. for small details i have been using the plastic clay to make small detail parts, like attaching buttons to toothpicks for landing gear,changing the appearence of small toy soldiers i use to make pilots in different scales, been using clay as filler on the fusalages, after i make what i want out of clay i give it a coating of crazy glue to harden it up, if i need to hold something to position it i use acrylic caulk, scrape the excess and give that a coating of cg, i buy the clay caulk and glue at dollar tree,and u can find some balsa (guillow eagle glider) there
I once tried to harden some balsa but gave up. Thanks for the tip.
Lou