My college roommate was wanting a painting from me for a room she was redecorating and we came up with an experiment that worked well. She brought a canvas and we painted together. She's not a painter, but she is fearless. We worked both simultaneously and took turns. We loved the painting after about five hours of work and then tweeked it some the next day. It's now hanging happily in her room.
If you're interested in a collaboration and are driving distance from New Boston, New Hampshire, let's discuss.