I believe Van Gogh painted with his right hand. His self portrait shows him with the brushes in his left hand because it looked that way in the mirror he was looking at. Also, one of his self portraits shows his right ear covered when in actuality he cut his left ear. Again, the portrait is a mirror image of himself.

Regarding Van Gogh's self portrait and the use of a photograph: Because the self portrait was done using his reflection in a mirror a photograph would not have helped as his portrait should have been a mirror image of his true self. However, if the self portrait corresponds directly to the photograph, it seems likely that he used the photograph and not the mirror to paint his picture. Hope this makes sense to the reader.