What exactly is anodising...
Hi Martin,
I will take a crack at this. Anodizing is an electro-chemical process by which the natural oxide layer on aluminium is thickened. There are 3 levels of anodizing: regular, large and super-sized... NOT! (heh... that's my tummy talking there :lol ) Ok, there are 3 levels of anodizing in terms of how tough and resistant-to-wear the final results are: regular, hard anodized (my machinist estimates that it is near 60 on the Rockwell scale), and Mil-Spec (E.g. SureFire's Type III Hard Anodized).
As the anodized layer is porous, it allows for the item to be dyed in the color of choice thereafter. If the item is not dyed, it retains its natural finish.
I am not sure if you can anodize aluminium DIY--cost-effectively, at least.
If you are going to send off your face plates for anodizing, be sure to let them know that your purpose is ornamental. Sometimes there might be mounting marks on the item as a result of the process.
There is another process called alodine, which supposedly gives another electrical property to the item alodined (shields it from something... which I can't remember).
Make sure you do everything you need to do to the item before sending it to be anodized. That includes drilling, sanding, and brushing.
Hope that helps!

Cheers,
-Lost81