Today I have restored to a better looking (not perfect) side panels. If you don’t want to remove the panels you can do the work with the panels installed in the car. It take me about 1 hour and a half to restore a single panel. These are the steps I followed (I am not responsible if damage occurs, just worked for me):
1 - Clean de the sail panel
2 - Mask the frames with painting tape
3 - Sand the panel using this order of water sand papers: 600, 800, 1000, 1500, 2000, 2500, adding water, don’t let the plastic get dry. Add water, sand the surface, clean with cloth or soft paper and repeat. From 600 to 2500, I sanded about four times with each sandpaper, it depends of your panel. When sanding the panel will lose all its shine and will look very ugly, it is normal
4 - Clean and add a few points of polish compound to the surface of the panel and use a polishing felt or polinish cloth. I used a polishing felt with adaptor for drill that comes with headlight polish kit. If you use a drill don’t spin too fast, portable drill/less power for me worked well. Clean and repeat until you get a mirror/like looking.
5 - I have not used varnish to protect the plastic but I think is necessary to apply and polish again to avoid orange peel. I think original sail has a coating, the one that peels out.
As you can see, it is the same as polishing headlights.
I bought a sandpaper lot from Amazon, very cheap and I used Meguiars Ultimate Polish Compound.
I think the finish is correct if you don’t want to remove the sail panels and don’t need a perfect/scratch free panel.