Prepping trailer for primer

What's the best way to prep my homebuilt trailer for prime? Some rust, lots of black steel oily protective stuff, some prepainted pieces like the axle and coupler, many bad welds, way too much weight, not square, bad tires, etc...You know the type.
Anyway, I wasn't going to go fancy on the paint, just Rustoleum prime and black spray paint. Are there better coating products out there that I should consider?

Anyway, I wasn't going to go fancy on the paint, just Rustoleum prime and black spray paint. Are there better coating products out there that I should consider?