Another Painting Question

O.K. another painting question:

All aluminum sailplane, newly constructed.
1. Scuff with Scotchbrite pads, two part epoxy primer, wet sand,
paint? or...
2. Two part acid etch wash primer, epoxy primer, sand and paint? or...
3. Your recommendation

I was once told by a venerable aircraft builder to attempt to use a
paint process like the Schweizers (sailplane fame)used but cannot find
out what that process was/is. He said that it was subcontracted to
Grumman and they "got it right".

And, where does Zinc Chromate fit into the picture in terms of the
paint process.

Confused as ever.

Clark