First off, I agree with the above regarding painting areas you just can't get to later such as underbody, interior shell and firewall because they now have parts attached to them.

Regarding the exterior - this is the subject of debate with no correct answers, just personal preferences.

The factory and every professional nut and bolt restoration company I have seen paints the shell inside and out before any assembly.

Me? Paintjobs are major expenses these days. Having to tow a body shell to a shop and then to require them to move it around on a dolly while they do the bodywork and paint is only going to make it even more expensive. My preference is to be able to drive the car to the body shop myself.

Then there is the sub-question about exterior paint with the front clip on or not - another debate without a "correct" answer. I am leaning toward front clip off the shell and reassembled after. Kind of a compromise with "paint the bare shell 1st".

Regarding how to put the car back together - I highly recommend this website that narrates how GM put these cars together. The Factory Assembly manuals are not arranged in assembly order.

1st Gen Camaro Assembly Process