Unfortunately the plastic used to make the canopies does not take to polishing. It's too rubbery. You can only get a hard shine on hard materials. Try the Novus polish system if anything. Another thing to consider is spraying it over with Future floor polish. It is a clear acrylic and is commonly used as a gloss coat in model making. It removes with anything amonia based like window cleaner.

The Future is worth a try if your not up against nitro. It can be brushed on and still turn out the same. Its self leveling and easily removable if you dont like it. It will hide all the fog and fine scratches.