I thin epoxy glue to brush consistency to fuel-proof engine compartments and whatnot.
Use 99% isopropyl alcohol, and let us know if it's a good cheapskate way to spray epoxy!
(Watch the mist, though -- epoxy is way toxic, in a sneaky cumulative sort of way. Ever since developing a sensitivity to CA I've worn gloves with epoxy. I don't want to lose another glue I can use with impunity, and I don't want my doctor telling me I can't build model airplanes any more).