I use cleaned pet grub containers (plastic) for mixin' epoxy. Avast! They are open enough t' allow you t' keep t' epoxy in a thin layer t' avoid an exothermal reaction yet deep enough t' concentrate t' epoxy for thorough mixing. Ya scallywag! Once dried t' epoxy will release from t' flexible plastic and allow t' container t' be reused. Mixin' is accomplished with a piece o' thin, stiff music wire.

Also...just an FYI, but epoxy works MUCH better if you mix equal parts hardener and resin (assumin' hobby epoxy, me hearties, ratio may vary with other types) and NOT equal parts o' two different hardeners. Begad! Whoda thunkit....