To teach the paw touch is to put a treat under something, like a plastic lid to a container. When he paws at the lid to get the treat, praise and treat. You can lift the lid and let him take the treat. When he’s touching the lid with his paw consistently, don’t put the treat under the lid and when he paws it, give the treat from your hand. Now you can replace the object with a light or anything that the dog can paw and it either makes a noise or turns on. To teach the dog to interrupt your behavior, sit in a chair and put the lid on your leg and give the command “paw”. When he paws at your leg, reward.
Another way to teach paw is to start by teaching your dog to shake. This will teach him to use his paws. Have your dog sit and put your hand gently on his paw. If he picks up the paw you’re touching, tell him yes and reward. You can also hold something of value and wait for him to take his paw and let you know he wants it. Give a treat and repeat.