First of all, learning to handle epoxy is probably exactly one complete half of learning to build boats. The good news is that it comes pretty quickly. You'll be an expert after only half a dozen boats. :D

Air compressors aren't risky if you use and maintain 'em properly. Good regulator, water traps, that sorta thing. It's always a good idea to know and understand ALL your tools and materials, so read the tech literature that comes with all your stuff. Not sayin' you have to know it by heart, but at least look over it and check out any items of immediate interest that jump up at you......

Epoxy is famous for its rather intense dislike of oily contaminations, but little else. So, are you running a kerosene heater per chance? Using any sort of bug spray? Anything else going on that might be depositing some sort of residue on the surface that the epoxy doesn't like? That's certainly what it sounds like.....

: First coat goes on smooth with a squeegee. When I want smooth fill
: coats, I use a low-nap roller, as supplied by kayak kit
: suppliers (cut in half, to 3 or 3 1/2 inches).

: But, there are others here with far more epoxy experience than
: myself. Mainly, I wanted to address using an air compressor
: between epoxy coats. Yeech! You're lucky if there's just
: moisture in that system. Might be oil. Very risky and
: unsanitary.