A depletion batch is when I want to squeeze the last medicinal benefits from my material. This is usually something that has already been extracted once like rosin chips or bubble hash.
Basically using the freezer like I normally do, I wash the material once for 5 minutes, then strain into the next container of material for 5 minutes and so on.
Ill typically use thia for topicals or capsules. I'll put a tutorial up later.