I don’t know if this is common knowledge or not, so I am going to share it in case it is useful. I had a fairly deep scratch (probably should have taken a before picture but I didn’t think of it at the time) in the plastic of one of the center gauges in my 3000gt, so i sanded out the scratch with 1500 grit sandpaper and used one of those generic headlight lens restorers (I used the Turtle Wax brand) on the plastic and it looks a lot better than it used to. Only problem is it has a lot of very tiny scratches on the surface from the sandpaper that are only visible if the light catches it the wrong way, but overall it looks pretty good. If anyone has some advice as to how to get it to look perfect with no scratches, feel free to comment.
I’ve learned from ChrisFix how amazing Ceramic Coating is. The stuff is pretty impressive not only for just your paint surfaces. The stuff is pricey though… there’s got to be some alternatives perhaps someone else will chime in on! Nice work by the way, always feels good to do any job on our cars.
You’re on the right track buddy but 1500 grit is the starting grade and will leave scratches equivalent to 1500 grit. Before you polish, you need to sand again with something finer like 2500 and water and if you want a perfect finish, go to 5000 with water and then polish if needed.
Remember to polish the surface evenly and lightly so you don’t create an un-even finish.
Maybe following the same process as restoring plastic head lights helps. You can practice first with old cassette jewel cases