Coating Rifle Or Shotgun

[wingwalker]

I would like to coat a couple old rifles I have. Not going to do the internal parts or action parts, just the outside.
Not sure which powder to use or color for that matter.
Would I have to take it down to bare metal of just clean it and coat over the blueing?
What are the best plugs to use in the ends?
Also do I have to worry about the temp. warping it?
Any sites that deal with this?

Thanks,