Here is my experience with diy of my metaltech rock sliders...
I too thought I could save money by doing it myself. I thought that it would be quick and easy. Especially at the time I had a new born and I hadn't wrenched in a while on anything.
I should have listened to myself that over the many many years of being a grease monkey that paint is hard to do well. The metaltech sliders still had the milscale on the tubing as well as well as any oil left to keep the raw steal from rusting. I went through countless 1 gallon acetone bottles from home depot to try to get the mill scale off. I then resorted to soapy hot water, then tried vinegar and anything I could Google search. This took me 4 days to prep the sliders while working on a bunch of cardboard laid out on the floor of my garage.
I then bought 3 cans of primer and ended up buying another 4 cans of vht matte epoxy paint. Primer I think was 5.99 a can at pepboys, the vht paint was 7.99 I think... I also had to drive around to 2 pepboys to find enough rattle can. The acetone was 3.99 at home depot, I went through 4 cans of it.
After painting primer and 3 coats of paint I mounted the sliders carefully. The first step I put my foot on the sliders to see, a chunk of paint came off. I was pissed. 2 weekends wasted, back was sore and I spent around $80 to $90 on paint and it all needed to be redone. I thought I prepped the sliders perfectly and made sure the metal was clean... But I guess not.
I was quoted 130 bux to have them powder coated locally here in San Jose. I ultimately unbolted the sliders and dropped them off to be sandblasted and powder coating after living with rusty sliders for a year.
Morale of the story. Get them powder coated. The powder coating is way stronger than rattle can and the pros have a way of sandblasting, dipping, prepping better than you can do at home.
I now just touch up with por15 and a bit of rattle can for overcoat as needed. So far the powder coating has held up very very well.