I use cheap spray paint; flat black rustoleum. If you actually plan to scrape them on things, you'll need to touch them up every few months to keep rust at bay and this stuff blends well.
That rough textured bed liner stuff will chip off and look like crap when you spray over it.
If it's a mall crawler (no offense) get them powder-coated and they'll shine nice for a long time.
FWIW; My '06 came with RSG sliders; bolt on. They did not seem hold the weight of the vehicle, even lightly set onto on jack stands (minimal shock load) tey shifted up about 1" in the rear. It was a PITA to get them straight again and they were torqued down pretty good. I'd suggest welding them on if you can, they'll hold up much better. My Tundra has weld-on sliders, and it weighs about 8,000 lbs with my FWC. I can jack the entire side of truck directly on them with a Hi-Lift.
