Everything I know about lighting is in my post:
http://forum.portraitartist.com/show...=1077#post1077
Sometimes I photograph my paintings in much the way that I photograph people. Sometimes I photograph my paintings outdoors in the shade. I never use a flash.
Of course the Old Masters did not have any lighting systems...but they had large studios with controlled light...something that most of us do not have. I guess it is a trade-off.