What are the best lights to use with a copy stand

I recently purchased a copy stand in order to digitize my company’s watercolor library. I am using 2 rps cl150 arm-light attachments however I keep getting 2 large spotlights on the paintings where the lights isn’t diffusing evenly. I have tried pulling the lights farther out, but it drastically darkens the photograph and still getting poor results when I place a white cloth over the bulbs. If anyone has any insight into what I am doing wrong or if there is a better alternative – bulbs, lighting equipment, etc – it would be extremely helpful.