When Daniel leaves the pool supply store carrying four cans of paint or sealant, (two gallons in each hand) no veins, muscles or ligaments in his arms react physically as they would carrying that much weight. No matter how strong he is, muscles and veins would change dramatically. Obviously the cans were empty.
When Daniel is repainting the pool after speaking to Amantha about moving out, it is quite obvious there is no paint on the roller. There are no wet marks where Daniel is rolling.