[jaynjeep]

The Sherwin Williams paint should spray just fine as long as you mix it and thin it properly... Use a hardener for quicker dry time and better longevity..
Get a large flat area and practice before you start on the tractor..

My dad used to spray a lot of enamel... his trick was on the last coat spray a half and half mixture of thinner with paint... that would help the final coat really lay out flat and make it shine..

I do like the more modern urethane paint for it's better durability and hardness but it is expensive and not as easy to spray for a beginner...

I would say the Irongard or an enamel like you have may be better for a first time spray project..

Don't be scared of it... practice makes perfect!!

Good luck!! I admire you for wanting to learn!