Honestly, i've used Rustoleum (up here it's called Tremclad) and brushed it onto the housing straight from the can, and it smoothed out like it was sprayed on there.
Very shiny and smooth finish and it still looks like it was done yesterday even though it was 4 years ago.
I buffed the housing with an aggressive cup wire wheel on a mini grinder and it hasn't chipped or flaked off yet or even dulled.
If you do it when the housing is cold, the brush marks might stay, but i used a torch on it until it was warm to the touch if that matters to you.
It cost me under 20 bucks overall and i am obviously happy with the results............
