like outlaw, i try to keep anything i am rattle-canning, and going for a gloss finish perpendicular with the ground. most every type of rattle paint i have used, the thicker it is laid on, the better your finish will be. and like outlaw also said, having it laid flat keeps the runs away when laying thick.
im no pro painter, but i have done some damn good rattle can jobs. i would say there is definitely no need to get a gun and all that jive. just practice on a similar surface, so you can get your sweep, distance and speed right, and you can lay some paint with a rattle can.