I didn't get it done myself, but when I bought my Z1 project the seller told me that the frame had been 'shot blasted' before professionally painting with gloss black. I was a bit alarmed at the thought of such a coarse media being used to blast a frame, but the finish is perfect, showing every tiny detail but no imperfections. It's also much more original looking than a thick powder coat.
Where it had been masked before paint, such as the threaded studs that the rear shocks mount on, there is very little metal 'missing' but a uniform matt grey finish. You can just about see that in the photo. Sadly I have no more information about who did the job, what it cost or what was used, but the end result was excellent.

I'm more of a wire brush and rattle can man myself, that's what my CL450 got. Cheap but factory looking, although original Honda frame paint always struck me as not that great, I've never noticed any primer under what appears to be one coat of gloss black.
