Well in my opinion\experience smoothness is the enemy of proper adhesion. When I was first starting to pc, I tried to coat a chrome derby cover for a harley. Worked and looked good but the pc would chip easily. I sandblasted to etch the surface, not remove the chrome, than recoated and the pc stood up to abuse like a pc'ed part should.
I've done some candy's but not anything like the silver you are looking at. I think we may be talking two different things. Your pc'er might be talking about larger gauges\imperfections on the frame. What I'm saying is that the part needs to be etched in some way, either by sanding or blasting to give it rough surface to adhere too. PC intially adheres to the part through electrostatic charge. Then the baking melts the pc onto the part where it needs some sort of roughness to adhere to. Otherwise it will be a layer of pc sitting on top of the part just waiting to be chipped off. I hope that makes sense.
The powdercoat will take care of smoothing out the final surface. It should get to a point where it melts, flows out and levels itself. If you have the right amount of pc and keep it in the flowing stage the right amount of time, the final surface should be smooth.
There is much more info on powdercoating over on caswellplating.com. This thread in particular has the steps for proper pc'ing.
http://forum.caswellplating.com/powder-coating-questions/13749-recommended-process.htmlIf I can dig 'em up, I'll find some pics of some parts I've done. I should have before, during and after of some projects. It'll show you the etched surface I'm talking about.
You can also sand blast the part, use a base coat of silver to get a smoother surface than coat with the metallic. The second coat will adhere to the first coat even if it is pretty smooth. It'll basically melt together. I've used a primer coat before to smooth out some rough parts, but primer is usually gray and may dull you metallic finish.
Hey I found a pic of a wheel we did. It was chrome, than etched with sandblasting than pc a mirror black. Came out pretty smooth although it started out etched. And lo and behold I also have a picture of the frame (Done by a buddy, but I taught him everything he knows...about pc'ing at least). Also the tank and headlight ears were done by us too. Don't say anything about the seat...it's a work in progress...
Good luck...
Matt