when it comes to writing.
I actually still use the Dupli-Color bedliner, it's the spray on Plasti-Dip
that I tried as a top coat and a clear that I didn't like.
The bedliner I use is Dupli-Color Bed Armor truck bed liner, I get it at an auto parts store in a 16.5oz spray can. http://contentinfo.autozone.com/znetcs/product-info/en/US/dup/BAA2010/image/4/
I've never tried any of the other brands, but they likely work fine also.
When I'm doing a wood stock or grips with the Dupli-Color I usually don't use primer, I strip the old finish and do any shaping or filling needed, then lightly sand with 80, 100, and 120 grit sand paper, then back to 100, and occasionally 80 grit again. The goal isn't to get rid of all the imperfections, just the big ones, and to knock down any filler and get a uniform appearance. The bedliner usually does a pretty good job of filling small stuff.
The wood should be slightly rough to the touch when you run your hand over it, but not enough to catch threads on a smooth dry cloth. If it's to smooth the bedliner can peel. Then I blow it off with a compressor and wipe it all down with a dry cotton cloth (old T-shirts work well), then start coating it with the bedliner. I usually let mine cure for a week or so before I put the gun back together, I don't know if it needs that long, it's just a personal preference.
If I do end up needing a primer I've had good luck just using the clear adhesion promoter in the rattle can. I don't usually clear coat it but it's done the same as any thing else that gets clear.
Metal can be rough sanded/primed, or both, and plastic and fiberglass work with the adhesion promoter.
I've done several sets of plasic grips and have been happy with them also.
Hopefully this is understandable, if not let me know. The only air rifle I still have that I did this way is one of my QB AR2078's, I have to dig the camera out tomorrow anyway so I'll get a picture of it posted tomorrow.