Painting in small spaces is always tricky, and getting behind the toilet can be a real pain. Luckily there are few tools ...
His system uses a 1 hp motor to pump paint from the bucket directly into the brush. Once it enters the handle a distributor splits the flow into four parts so that it reaches the bristles evenly.
I grew up in Connecticut, where taste in paint brushes (and paint) runs toward the traditional. So I started with big oval handle paint brushes and angled trim brushes and that was that.