ORIGINAL: j.duncker
Get a pad of 2 inch square post it notes and a barrel of toothpicks.
Mix, use and discard.
I do similar except I cut up old catalogs (the kind that have glue binding, not staples) into square pads and use either toothpicks (flat kind) or match sticks for bigger mixing jobs. The soda can sounds like a good idea for those times when you want more working time. Thanks for the tip.