For oil paintings (not that there should be too much difference), I have used Fuji Astia F, but only in soft overcast conditions outdoors with the correct warm up filter. The artists have preffered this because it depicts the texture of the paint so long as the orientation can be made to match the lighting direction of the painting itself. Of course you become dependent on waiting for the correct weather before you can proceed, not usually a problem here in the UK!

Colours and contrast seem pretty accurate, most importantly the artists and gallery owners have been happy with the results. I Blu-tack either an Opticard (White, grey, black) or Kodak test card onto the edge of the frame as a reference. Thus should it need to be scanned or sent for repro, any deviation of colour or contrast can be corrected. I shoot 2 sheets for each and push/pull second one if necessary.