i laid mine on a saw horse, that way you dont have to move or touch it. if need be put blocks under the saw horse legs to lift it higher. the one i used has adjustable legs, i had them maxed out.
only tips i can give is light coats with a 50% over lap. keep the can as even as possible with the surface with each pass. 8 to 10 inches. if a spot looks to light f it, the next coat will cover it. trying to fix stuff while painting will only get you in trouble. keeping the speed each pass is also key to how light or not your putting it down. make a few passes on cardboard, this will let you get the feel a bit. and see how much is coming out at what speeds. clear the spray tip after each coat too, turn the can upside down, and spray for like 3 to 5 seconds, then before the next coat, spray the card board before the bumper, this makes sure it wont splatter out the spray tip.
worked the sides first, when i came to the turn of the bumper i passed it right by, then cut the spray off, start spraying before the bumper and start the 50% over laps.
i did both sides, then the long ass middle part, over spraying past the turn of the bumper. so its like painting 3 parts.
always have the spray spraying as you come to your work, then stop after you passed the work. seems like a waste but its what works.
and prep, wash it good, then use a scotch bright pad or some 600 grit wet sand paper to scuff the paint up, then use duplicolor prep spray cleaner, this gets rid of any grease, tar, oil from your hands, or wax. wipe it down, let it dry, and have at it with the paint.
good luck, my the painting force be with you.