Bill absolutely did not invent wet on wet painting, nor any of the techniques he used, I mean not one of them.
He (or the company) could trademark names, like Magic White, and maybe specific images he created, but other than that forget it.
was the best wet on wet painter I have ever seen. I adore his art. He used the same big brushes and big knifes, in the same way as Bill and Bob, and threw in some other stuff I never saw them do, like taping off those Bluegum trees in one of his videos. Bob used to tape off vignettes though.
From South Africa, he probably never knew who Bill was, and was using those techniques before Bill had a show.