Spray bombs can turn out satisfactory, most don't though.
You have to use good paint (OP is painting is black so probably not). A car I used to own was sprayed white with some expensive stuff from autozone (like $8 a can) and it came out good for the money spent. Nothing like real automotive paint though...
Prep and prime and put a bunch of coats on.
I know rustoluem makes all kinds of different stuff that come out decent.
So please explain how walking the length of a car while keeping the can shaken enough to spray even is going to turn out good? There is no way and even if you spent the time and money to make it look half ass even you may as well have just bought the stuff to do it correctly.