Need help with prepping for paint

[juntari]

I'm working on a helmet that is cast in smooth cast 300. I sanded it smooth with 200 grit sandpaper. I started wet sanding with 600 grit but stopped because I was worried the paint wouldn't stick. So my question:

Should I
1) wet sand everything, prime, paint,
2) prime, wet sand, paint or
3) prime, paint, wet sand?

Also I have some small bumps over the larger areas, my fault for not smoothing out the clay perfectly, but what is the best way to even that out? Its a long smooth curve, hand sanding hasn't really helped reduce it and I'm worried a power sander would just flatten spots. Any suggestions? Would a power sander be gentle enough?

 

[Finhead]

Only way to get something smooth and straight (even on a curved surface) use a block to sand with. You can't get it straight by hand because your hand/fingers fallow the piece.
You should sand everything straight, prime then sand/wet sand then paint. Your paint should have no issues sticking to 600 wet, I blen out with 1000 grit all the time and I only finish with 600 wet on a metallic.

I'm working on a helmet that is cast in smooth cast 300. I sanded it smooth with 200 grit sandpaper. I started wet sanding with 600 grit but stopped because I was worried the paint wouldn't stick. So my question:

Should I
1) wet sand everything, prime, paint,
2) prime, wet sand, paint or
3) prime, paint, wet sand?

Also I have some small bumps over the larger areas, my fault for not smoothing out the clay perfectly, but what is the best way to even that out? Its a long smooth curve, hand sanding hasn't really helped reduce it and I'm worried a power sander would just flatten spots. Any suggestions? Would a power sander be gentle enough?

 

[exoray]

As said don't worry about primer sticking to a 600 grit sanded surface... Generally for my first coat on a fresh casting I recommend people wet sand in a tub of soapy dish water, the soap will clean any left over release, oils or what not and also aid in the sanding... Rinse well, dry and then prime...