Andy, I've been enjoying watching the process of your MTB frame with some original ideas on the frame was well as how it is made. It is certainly nothing you could buy in a store. BTW, I encourage my frame building class students to put their frame together to ride it 1st before painting it for real just to make sure all the braze-on bits are in the right place and they haven't left one off they now wish they had. As you already stated, a clear coat over bare metal won't last long but I'm sure long enough to figure out if you need to make any changes. You might want to consider putting on just a primer instead. House of Kolor primers that come in red, blue, yellow as well as black and white are actually nice colors and might be another option for you. Because they are primary colors, they can be mixed to make almost any color.