: Be careful thinning epoxy, as too much solvent will result in a
: 'rubbery' result.

I had some epoxy/solvent mixture sitting in a jar I was using to clean brushes a while back, it turned into a weird epoxy jelly for a few weeks before finally hardening, presumably less dense/strong as pure epoxy. This was of course probably 50-80% solvent, but I could imagine that an overly thinned epoxy would take a lot longer to cure totally (and may never be as hard as pure resin.

I also vote for warming the resin up to reduce viscosity. I've been doing a lot of work in the garage this winter and I generally keep the resin inside if I want it to be viscous enough to wet-out glass. In the summer I had to thicken it because it was too runny.