i do something similar to bill--use the plastic lids from coffee cans--then you can peel it right off.
if you do not mix it properly and the epoxy is still a bit sticky after it 'dries' coat it with clear nail polish.
i've read that using wood to stir epoxy will cause it to yellow. not sure if that is true but i always use metal.
if you ever buy the type that comes in one container with the plunger, split the handle of the plunger to give you more control of each side.