Check out their Web site at http://www.westsystem.com. A good page on that site is http://www.westsystem.com/frames/tier1/usingepoxy.htm ...describes the various consistencies of epoxy with filler: Peanut Butter, Mayonaise, etc. You don't have to be exact.

Peanut Butter is good for small gaps and fillets, thinner consistencies are said to help keep all the epoxy from flowing out of a joint. Best practice is to coat surfaces (especially end-grain) with unthickened epoxy, add filler to taste and reapply : )

Good Luck,
Chip

PS: I thought that much heat made any epoxy fail.