For implements that will be drug around in and through the ground, I use Dupont Industrial Imron 2.7 pr (primer) and 3.5 HG. Used it on a backhoe bucket and it's held up great digging. Toughest stuff I've found. I spray it with a pressurized gal pot and an HVLP gun from Hobo-freight. Good enough for implements ! But a supplied air helmet or 1/2 face mask with goggles is needed due to the hardener.
FYI - hardeners have pretty much the same stuff as super glue. It's activated with moisture. When you breath it, it will coat the little tiny openings in your lungs and seal them off -- permanently. It's like getting an instant permanent asthma attack that CAN'T BE CURED short of a lung transplant. Do not spray hardened paints without proper safety equipment.
For a tractor touch up, color from the mfg is good sprayed out of a touch up gun.