I second DARKFLY on the 'clean enough to eat off'.
80% of the work of any GOOD paint job should be the preparation. If the substrate isn't clean, nothing will stick to it permanently.
And, trapped rust will continue to eat farther into the iron/steel, hidden by the coating.
Use GOOD grade of rattle-can. There IS a difference, and you get what you pay for.
Cheap paints = mostly solvents that evaporate.
Good Paint = Lots of 'solids' that remain to form a coating.
Conversion primers: Expensive, but worth their weight in gold at 'converting' light rust into a dense coating that can then be painted with oil-based primers/paint
Paint job = Primer + paint.
Primer: Stuff that sticks well to the substrate, but won't standup well to to sun and water.
Paint: Stuff that stands up to sun and water and oil, but doesn't stick well to bare metal.
Put a coat or two of good primer onto the metal. Allow to dry according to directions. Then finish with a couple coats of good paint.
Good luck.
-Rick