I brushed the paint on, but if I were to do it all over again, I'd just buy spray cans. And if I did brush paint an engine again, I'd either use better quality brushes, or use sponges. I bought cheap brushes because I wanted to just throw them away when done, but I ended up picking loose bristles out of the paint. That's what I get for going the cheap route I suppose.
Next time use sticky tape on the bristles. It will pull off the loose ones before you dip into the paint. I use the cheap chip brushes this way.