Nick already hit most of these; I'll only expand on the heat the epoxy issue:

: Does heating the containers of the stuff help?
: Will coats of varnish fill the sanded off bubbles?
: How many coats should I put on the inside?
: What does amine blush look/feel like?

I built a box out of 3/4 plywood, which I heated with heating pad and a 60 W
light bulb -- in a 40 - 50 degree shop. (Produced 80 - 90 F temp inside the
box.) This kept the epoxy nice and thin for
mixing, but left it with enough pot life (small batches, anyway) to be
manageable. I should mention that I had the yak I was building in a separate,
heatable space (to 60 - 65 F). I tried using the 40 - 50 F shop, but even with
a 1500 W electric space heater directed onto the work, the yak was just too cold
for the resin to flow or wet out the glass.

On the bubbles -- Nick gave me some advice a long time ago which has worked really
well: preheat the work surface for a couple hours to a temp just a few degrees
ABOVE the anticipated cure temp. AS YOU LAY ON RESIN, turn off the extra heat.

This will cause the gases in the wood to contract, and "suck" the resin INTO the
pinholes, sealing them forever. Pinholes are such a major pain in later coats of
resin or varnish, it is worth an extra coat of resin to get rid of them!

Dave