Oil and Acrylic paintings, along with any other types of "flat" art that have textured surfaces, post some interesting options that require a more specific setup than conventional copywork. My recommendations are:
1. Use a very long lens so that your working distance is at least 2-3x times, and preferably 4-8x, the diagonal measure of the painting.
2. Take complete control of the lighting. You need a minimum of two evenly spaced lights that strike the edge of the painting at and angle of 40-45 degress from the plane of the painting (45-50 degrees from the lens to center of painting angle). This angle might be different, particularly when you can use a properly long lens. With a long lens, the angle from the plane of the painting should be greater (closer to camera's line of sight.
3. The lights and camera should both have polarizers. The lights should have identical orientation to each other and the camera's should be 90 degress from that of the lights. The idea is than no light should reach the lens other than what is diffusely reflected from the painting.
4. If you wish to show the brush strokes, a single unpolarized light should be place at a low angle (close to the plane of the painting) to skim the tops of the brush strokes. This light needs to be at a distance from the near corner of the painting equal to about 8-10x the diagonal measure of the painting.
The reasoning for the above is that the long lens reduces the angular difference in the view at each corner and the center. Seeing one brush stroke from slightly below and another, at the other side of the painting, from above creates and artificial look. The distance to the copy lights is so that the lighting is reasonably uniform across the image. The placement of the lights is to minimize reflections, though with shiney oils and acrylics there will always be some. The crossed polarizers are to eliminate reflections further. The accent light (#4) needs to be so far away because it must not be detectably brighter at the near side/corner comparted to the far side; the 10x factor will reduce the difference to 1/2 stop or less.