NIce truck Danzig

My opinion of course,
but, consider buying some quality, (but cheap) tractor or implement paint sold at tractor or farm supply stores; and compatible primer/sealer. I believe that Rustoleum and Valspar both make this type of paint and package it in quart cans.
They come in all sorts of colors including black; so you can approximate the original color in two tone like you have it now.
I think that you'll find that enough rattle cans will cost a small fortune and these types of paints when purchased in quart cans will be more economical. Results will be way better than the splotchy look of rattle can paint.
Now, you'd have to borrow or rent a compressor & spray gun, but I think you'd get a reputable job (better than rattle cans).

As far as prep, after thorough washing and cleaning, I'd invest in a can of wax and grease remover. Section at a time start wiping it down then sand that area down till it's scuffed up real good... You don't need to go down to bare metal; just enough to provide some "tooth" for the new primer/paint and expose the areas needing filler or repair. As for repairing dings... fill and level them with a good quality product like
EverCoat makes ...you can find a gallon their filler for $20 or so.

Once you get the truck prepped and masked off ; you can pop for the spray outfit rental and shoot it in one day...

my 2 cents!
mike