It basically works the same way as a wet dry...actually more efficient because you're losing less flow from pump "head"...
I have a bunch of "dump" filters in my fishroom. I prefer to use clear Rubbermaid containers vs. buckets as they fit on top of the tank (or a corner of it) and are easier to see what's going on / clean.
My favorite design uses one of those three drawer plastic storage containers sitting in a rubbermaid bin. Drill holes in the bottom of the trays (like drip plates), a hole in the top of the 3 draw container (for inflow from the pump) and 2-3 holes in the bottom of the rubbermaid for the water to dump back into the tank. Fill the first drawer with fluff and the 2nd and thrd with bio...
Basically, it's a wet dry without drilling your tank!
Matt