Yes, I have. Bob Ross is an old PBS stand-by, hard to miss. His are oil paintings, though, not acrylics :)

Yes, he painted oils. He used to paint over a wet mask, so gradients were very easy to do. We should paint with his technique someday. Don't you think?

Yes, I do that sometimes, using retarder. This particular doodle is painted on paper though, so getting it too wet is a bit of problem.