Plastic weld the little holes shut, you can use scrap pieces of ABS plastic, or even zip ties. Be sure to melt them in real good to the plastic body, and they'll bond like they are all one piece and never fall out. Then just use a little spot putty to fill the pin holes, sand, and paint.
IF the holes are irregular shaped, using a hole saw to make a perfect circle is a good idea. Then you can use the hole saw in a piece of spare ABS for a plug. Then plastic weld the plug into the body
All you need is a $3 harbor freight soldering iron, a chisel tip (or you can cut up a pocket screwdriver) and zip ties/spare bulk ABS