TinMan - That's what I do for the engine compartment. For the tank and radio compartment, I dumb in a couple ounces of Minwax solvent based polyurethane, slosh it around a bit and then drain it out - usually through the fuel line holes in the firewall.

Oh... I plug all the holes before I pour it in so I can turn the fuselage every which way without it dripping out everywhere. An acid brush helps me get it where it won't slosh.