Dan Bron wrote in a comment:

The word, extending your guild-theme, is master. As in master painter, master chef, chessmaster, the Dutch Masters, and so on. A journeyman is exactly the person who's pretty good at something but hasn't mastered it yet (the old guild system went apprentice -> journeyman -> master, which happened after the journeyman became sufficiently experienced to produce his masterpiece, the medieval analog of a master's thesis or doctoral thesis or that thing the art kids have to do to graduate).