This thread gives me courage and some ideas too. I just bought a New Braunfels Black Diamond last weekend. It has plenty of rust all around, although none of it has eaten deeply into the steel.
I purchased a 4 1/2" angle grinder and a wire cup brush at Harbor Freight Tools in Tempe. The purchase set me back all of $19 with tax. Better than using my good drill and a wire wheel.
I am intrigued by the color options available with the manifold paint. I will have to look into that.