VW T3 – painting

Good morning, my bulli should get a new varnish. I.e., old paint down, prime (with Corroless No1) and new paint up (by grinding, grinding, grinding…). So far I have the order… I have a HVLP gun with a 1.3 nozzle. Pressure I wanted to adjust to 2.5-3bar. The paint is a 1-component resin varnish (alkyd resin varnish). As this will be my first paintwork, I have a few questions. Up to what grain I have to prime up until I can a) prime? b) paint? And, with what grain do you start? Is there possibly a WWW site that can be used as a tutorial? I am aware that painting is a tricky thing and the result will not be 100%. But I try to do the project as well as possible… I will then upload a few previous photos here later. About a few tips I would be grateful…