heres what i mix on for small batches of glue.. I take an old catalog, like last years tower catalog, and I smear titebond type glue on all three edges that aren't bound. work it in a bit, then let it dry a day, then I cut it into 4 equal parts on my bandsaw, now I have four glue pads that I can mix on, just tear the top sheet or two off and toss them. Also a good way to mix small batches of epoxy is to make two equal lines of glue next to each other, but not touching, that way you can compare easier, and its not curing yet...

I used to mix in the waxed cups and never had a known problem with it, but I quit before I did have a failure...