Set as soon as you feel them--I don't necessarily agree that they'll spit it--after all bass are used to dining on hard objects like crabs and lobsters, and fish with spiny dorsals--but you increase the chances for deep hooking the fish if you wait.
They have enough of the jig in their mouths when you feel the tap--if you're fanning on the set, 99% of the time it's just small fish.
Wise men speak because they have something to say; Fools, because they have to say something.
The smaller fish seem to bump harder than the big ones most of the time. They are used to eating hard objects but I think a 4inch bait that weighs 4oz and is hard as a rock may seem suspicious and the larger fish are more cautious. My uncle is a fish ya know.
When I've fished them, I'm drifting in heavy current, and working the bottom. Rod goes up and down in fits and starts. After a strike, a little extra pull up and bingo. They seem to hook themselves through engulfing, too.