Your ok using sand paper, would try a 1000 grit wet sand paper and wet sand. Wet sanding is cleaner plus it provides lubrication to the sand paper making it easier to sand, and easier to remove the sanding residue, plus your not breathing it in, also keep in mind to start out with a fine grit sand paper like 1500 or 1000 grit, if you use an aggressive grit sand paper you may remove too much paint or even possibly remove the plastic in areas, also using a aggressive grit sand paper makes it harder to finish because you will have to move up two times sanding each with a smoother grit sand paper to remove deep sanding scratches. Also with a finer grit paper it may take you a bit longer but you will have more control on how much material you remove
