There are several YouTube videos on the subject, worth a watch. I think it is designed more for external sheet metal that will be top coated. From what I remember, the kit comes with a rattle can of 2k primer to get into the tight spots and edges that the roller can’t reach. Not sure exactly what the catalyst is, but I imagine it’s a combo of hardener and reducer. There are other epoxy primes out there, Sherman Williams makes one, no idea how it compares. For me it was easier and more cost effective to just use the spray since I would have to use the rattle can anyway with the roll on system. If you plan on topcoating then Eastwood is a good product, plus you have 7 days before it fully cures, after that you have to scuff the primer to get proper adhesion. Then again, if it’s just for internals you might be better off with a less expensive big box option like the Williams or just use Rustoleum. It’s an oil base, no catalyst needed, but you could reduce it with acetone. Let us know how it works out.