Tim Wescott wrote:

Rustoleum spray-bomb should work fine. Use their metal primer first,
then the color(s) of your choice. You _can_ do a good job with spray-can
paint, but not the first time you try.

Surface prep is Critical.

Clean! No dirt. Minimize surface oxides.

Degreased! Use lots of paint thinner to eliminate
finger oil for example. Change application cloths
often so that you don't simply smear grease around.

Dry! Paint the object, not the fluid on the object.

Temperature is Critical with rattlecan paint.
Rig up an Air Oven if you want your paint
to stick. Adjust the temperature of your
parts towards the high end of the recommended
temperature on the can.
When you ignore this advice, you will be
rewarded with a tacky surface that never really
dries and falls off under fingernail pressure.

An 'air oven' can be as simple as several flood lamps
aimed at your part from various angles. I used a
length of air duct with a floodlight inside.
It provided a nice convective flow of warm air through
the parts that prepared them for painting and
dried them properly after painting.

Paint only in a well ventilated area.

--Winston