Pat,
I tried Aluminum once or twice with no success. It's a technique that requires a lot of parctice, not nearly as easy as steel. I was making an antenna bracket for my Ford and realized that I'd be spending more time and material learning than if I just paid an expert.
I generally use Argon/CO2 mix rather than flux cored wire as I don't like to chip slag between passes. Though I'm informed that the flux cored wire works better outdoors as the shielding gas is easily carried away on a slight breeze.
Eastwood Company, a supplier of automobile restoration and body repair items, has several powdercoat guns and related items in their catalog. I can see your palce with a HOT PINK powdercoated porch railing! [img]/forums/images/icons/blush.gif[/img] They also have the radiant heaters available. I'm tempted to buy one just to play with. The guns start under $100. OK, not much under.