Rules on instants played at blocking step

So I know that as an attacker, I can play an instant after blockers are declared (technically at blocking, but before damage is assigned) but would this carry over to trample effects? For instance, I attack with a 20/20 (I mean big green stompy) and my opponent chump blocks with a 1/1 token. At the damage step, priority goes to the players again. Would I be able to at that point play an instant that gives trample, like [[charge through]], [[berserk]], etc, and still deal that trample damage to the player? Sorry if I'm messing up the names of the steps, haven't been playing that long, but hopefully I'm clear enough to be understood.