Only the paint roller down the hallway for now. Sit on the floor at the end of a hallway. Have Tank at your side or between your legs -- get his attention on the roller and toss it toward the end of the hall. If he picks it up, he has only two options : 1. Return to you with it or 2. Not retrieve.

And remember ONLY 3 or 4 retrieves per session (two sessions per day).