Shenzhen ping pong: serve plus two backhand, one forehand drill

Adding serve into the two backhand, one forehand drill. Stage 1: serve underspin. Partner pushes to backhand. Forehand loop to his backhand. He blocks to the forehand. Forehand loop down the line. Then he blocks to the backhand. Then Stage 2: two balls to the backhand, first one is the previous block: take first with your backhand, take second with your forehand. Then one ball to your forehand. And repeat stage 2.