For a cheap finish, 1200 degree engine block enamel works well. It's a lot tougher than BBQ grill paint, in my experience. Most auto parts stores have it in stock. After spraying, you'll need to bake your parts in the oven for at least 30 min at 350 or so in order for it to cure properly.
Alumahyde II is better and doesn't require baking, but it's more expensive and it takes around 2 weeks to fully cure. This means don't touch the parts AT ALL during this time.
Which ever you choose, the most important step is to degrease your parts thorougly before spraying.
