Guide to proper sanding / tools

Hi :

    I want to remind you that there many grits out there and it sounds like you started to fine . Now what I do is this .I start with 320 grit and plenty of water .Yup , You  want to wet sand for the best finish .Then , when those pesky rivets are gone , switch to 400 and then 600 grits .The model will then be ready for the final step . That is a good wet sanding with 800 grit or higher .Your model should then be as smooth as a baby's butt !

Wet sanding with a fine grit is my preferred method as this doesn't chew up the plastic quite as badly as dry sanding.   Wet polishing with an old cotton cloth can bring back that showroom shine to plastic as well.

I usually use the finest grit that will do the job.  And for any remaining scratches, one of  the functions of a primer is to fill in minor scratches.

Sounds like you started with an extra coarse grit. I usually start with a medium grit stick, not pressing down but rather letting the pad or stick do the job, then move up to finer grits up to a polishing stage following the contour of the repair area. I've found that if you press too hard deep scratches are created then and become very hard to remove. You may have to add some Mr. Surfacer to fill in the scratches then lightly sand. I also discovered that if you rub your finger nail across the sanded area, the plastic becomes polished and shiny. I then follow it up with the polishing grits. Walmart and the Dollar Store sell those multi grit padded sticks that are great and cheap.