Well, you may never be like them, but they both had the same advice on how to get better at anything you do.
Keep doing it. And do it a lot.
Seinfeld said the way to get better was to write jokes every day -- he made himself do it by putting a big red X on a giant wall calendar for every day he wrote. After a few weeks he didn't want to break the chain of X's. "Don't break the chain."
Monet's advice for improvement was, "Advise them to paint as they can and as much as they can without being afraid of poor results...If their painting does not improve of its own accord, then nothing can be done... and I could alter nothing."