I have discovered that antique dealers become too diverse in that they do not specialize in one item. There has not been a shop that I cannot find many sleepers. I would suggest staying out of the main stream of collectors of paintings and concentrate on dealers who coup de grass is furniture, glassware, paper, etc. They will stumble upon paintings within their purchases that they haven't a clue about the artist or the works. Mainly because they have purchased their favorites and the painting just was part of the lot.