I used grit 1200 as final sanding on a model. When I touch it, it feels smooth. After Air Brushing, sanded scratches appeared again. Any tips to remove it?

Couple options. Plastic polishing solution, available from an automotive supply store. Or try to find polishing pads in the car model department of your hobby shop. These will go progessively up to 16,000 grit and can polish out clear plastic better than it was molded. The car guys use this to get that glass like finish on their paint.

Al's absolutely correct. 1200 is actually fairly coarse for final sanding, IMHO. The first grit on my set of polishing pads is 2400 and it goes up to 12000. I'm not sure of the grit on my sanding sticks but I think 1200 is the Medium grit, with Fine and Extra Fine being a finer grit. I don't know what resources you have there in the Phillipines, but you can try to find a set of sanding sticks, Squadron and Flex-i-file are the ones I have, or look in a Health and Beauty Aids sections for nail buffing sticks as they usually have several grits on 1 stick.

I read on another site that rubbing ordinary toothpaste on the plastic polishes it nicely. The "grit" in toothpaste is especially fine - I have yet to try this, but it sounds pretty good.
Later-
Jeff