A few auto body questions

Not sure I have any 80grit discs but I do have 100grit disc would it be ok to go to that next? I went with the 50grit as im using an electric orbital sander and im sure its not as effective as an air powered DA.

I didnt mind the HF gun. I even bought a 1.8 tip for them for my primers. Just thought maybe this was the time to have something a bit better.

I see some sort of red primer on the bottom, followed by what looks to be 2 coats of grey (could be 1 but looks like 2) followed by top coat.