Bit of sandpaper to get that rust out, nothing too grainy so you dont take mega big scratches out. Wet and dry it to smooth everything out. Coat of that filla prima stuff. Wet n dry agen. Repeat until super sexy smooth.
Mask and paint. Rub down first paint if you want too with wet n dry. Laquer if needed. Oh and bang a bit of bodyfiller in any kurbs/dents.

Just my cheap tight barstuad method. Open to any criticism.