Not to speak for Mickie, but I think he brush paints all his fantastic looking buckets as does Journyman protector, you may want to contact them.
So it can be done.
For one tip, brush the paint on and let it dry, then lightly sand it down with very fine grit sand paper to get rid of the brush strokes, repeat the process as many times as needed until you get the desiderd coverage you want. I have done that in the past on projects and it works really great.
HTH,
Lynn