I've rattle canned a bunch of bicycles and most of my first 40. Primer is easy to make smooth, and can be easily sanded. Color is best in gloss without clear coat, and it is slightly harder to not have drips than primer. Smoothness is about planning edges in the process of paint application, because applying several light coats, or painting next to tacky paint isn't as smooth of a result as painting adjacent to truly wet paint. Clear coat is a rattle can disaster, especially evident on flat surfaces; I'm horrible at it. Be aware of paint accumulating on the rattle can orifice, it will cause drips. Same goes for your finger or a nitrile glove. I never sand to prep, but I use green Scotch Brite (to rough-up the surface) and acetone using dish-washing gloves (to remove oily waxy residues). I paint in the cool of morning and bake it in the intense heat of afternoon, so June thru August is the only proper time for a rattle can. I would skip primer unless I have a month of cure time, subsequent layers seem to promote chipping on layers of rattle can paint, particularly where I attatch my bicycle's cable-lock at the seat post, and the vulnerability of the top of the chain stay. Something like a Land Cruiser hood should be ideally painted in a vertical position, from top to bottom. Test your color, technique, and texture on a something like roof flashing. Rattle can mistakes often can be dealt with using acetone without damage to real paint. Don't fret over mistakes, and it is really better to under apply then to over apply. If you find a '73 40, with fuel door, upside down bezel, and hard-top, sporting Rustoleum 'Sand,' factory white fiberglass, and grey primer for a roof liner, that is likely a truck that I once owned.
I treated the surface rust with rust converter
