The vet suggested using a wet paper towel folded in half to pick up a frog... it helps you keep a steady grip (is less slippery) and prevents the frogs skin from absorbing chemicals. I'm still squeamish handling a frog so I use a flat plastic handle thing and sort of coax Chester forward with it until he climbs aboard. I use the plastic container and lid from my electric vegetable steamer, it has built-in ventilation holes and holds the moisture in perfectly.

(Boyfriend purchased a new steamer since then, lol)