Proper Sanding Grit?

Well Sir, it depends on what type of finish you're looking for. If you're only looking for something to remove small imperfections use 600 wet-or-dry sandpaper. This makes the smallest sanding marks that you can smooth things with, and paint over it without anything visible afterwards. This is what is used in the wet-sanding of automotive finishes to smooth out orange peel from the spraying process. It removes only tiny bits at a time, and can be controlled so that you get professional results without the worry of going too far. What you're using is too soft, and is meant for polishing - not shaping. Use hard grits for shaping, medium, and fine grits for smoothing, and ultra fine grits for polishing. Sandpaper is considered a supply, but it is also a tool! If you use it wisely you can do amazing things with it. This is what I use the most other than 60 grit, 200 grit, and 600 grit all the time for most of my modeling projects.

~ Cobra Chris