I have had a couple of difficult brake bleeding sessions. The best trick I found is to not just pump the brakes up and then open the bleeder when compressed but to always remember to pump the brake pedal or lever many times before starting the pump and purge process with the bleeder wide open. I think this gets the brake fluid and air moving towards the vent. Also add a length of flexible hose to the bleeder to catch the fluid and create a liquid trap.
Just keep trying and don't get any on the paint.