Painting Metal Door

[John J.]

Hey Guys,
Are there any tips or tricks to painting a metal entrance door. I sanded and prepped the surface then painted with rustoleum. The paint seemed very thick and got tacky quickly leaving brush marks, also 4 hours later certain spots seemed so shrivel up and leave fine ridges all over. Im sure there is a little trick or something. I was thinking of thinning the paint?

Thanks
NS