rattle can painting is really, really hard to make it look good. best way to do it is to use flat paint as it doesn't show the spray overlap nearly as much as gloss.
prep is the key to any paint job. everything is filled, leveled, sanded, rinsed, sanded again, etc. starting with a good self-etching primer after the body work is done, then going to a smooth primer after the sanding and leveling. cleaning everything with a paint prep thinner, then the paint. again, you really need a good paint gun, compressor, and place out of sun, wind, dust, etc. to make it look descent.
then lots more sanding between coats of paint, going to finer and finer grits of sand paper as you go. next you start the clear coat process. and after a few weeks work, you're done!
actually, you really should go the library and get a couple of books on body work and painting so you know what all is involved. it is way more than i just related to you.
but, as with everything else, time, patience, and persistence will get the job done for you.
good luck!