I find oil and acrylic paintings the most challenging, compared with other artwork, because those with heavy texture often generate specular reflection to excess, often no matter how I position the lights. In theory this can be dealt with by placing polarizers over the lights and "tuning" the reflections with a polarizer on the camera. The problem there, working as a hobbyist/volunteer for my local art club, is the rather high cost of polarizing material -- too much investment for rare occasional use. That said, I use four softboxes with large CFLs at 5500K as daylight (though I admit less and less with film) generally by playing with the softbox positioning I'm able to get results suitable for putting on the web, but likely questionable for real reproduction work.