Sanding grit depends on the job. What you you mentioned may be too fine for this job. 1000 is not for material removal.
The procedure is to find out the right grit for each job. If I've done a particular job before, I start with one grade finer than I think I should, on a small spot for testing. Based on how well the defects are removed and how fast I then decide if I go finer or coarser and by how much. If this is a new job that I'm not confident where to start I just err on finer grit and progress from there.
The right grit should remove all big defects, without leaving unnecessary deep scratches and without clogging, requiring excessive pressure or prolong sanding. Good sandpaper should cut clean and efficient, but not excessive.
Over the years I had jobs that required as low as 600 or even 400 grit on some sections.
Always wet sand never dry sand. Rise your sandpaper often. If it is not cutting well change sandpaper/grit, do not apply more pressure. Tip: add a bit of dish soap to the water but not too much that is foaming.
Always use a pad (foam). Never use your fingers as the pad if you want professional results.
I usually store a full assortment of sandpaper from 60 to 5000, so there is no job that we'll surprise me, lenses, paint, vanishes, you name it.
2k coat is what you want. PPF is not designed for headlights. There is similar material for headlights but it is thicker designed to be applied for the front, protecting against hits. It doesn't go well over ridges to cover the exfoliating top. You can use that for protection after you apply the clear.
There are many great clears, but most are designed for paint not headlights.
You want a clear that is crystal clear, dries very hard, and works well when sanded.
Yes, you need to wet sand the clear for pro results. The clear surface should be like glass when you are done. Procedure is the same like any car clear coat sanding and polishing.
You know you've done a great job when you can see all the defects inside the plastic and inside the lens surface.
Tip for clear application... make sure you degrease the lens! There should be no polishing residue or enything else. Mask the front of the car. A great 2k clear will have very fine and a lot of atomization. You'll see it as a very fine dust all over the place. You do not want that stuff landing on your paint. You do not want additional sanding and polishing work.
Take your time and mask stuff properly for sanding. Your goal is to protect surfaces that should not be sanded. Redo the masking before painting keeping in mind that unlike water and sandpaper paint could travels in all directions.
Good luck and do not rush the job.
