it isn't how hard they are to paint because that isn't hard. Its how often you have to paint them. Paint won't hold up as well as the powder coating, not by a long shot.
Paint process? Clean thoroughly, sand with 180 to even them out, then 360 to slick them up. I always lay the wheel down on the ground, paint side up and use dawn dish washing detergent on the tires to keep the paint from sticking to them. Squeeze it right out of the bottle straight onto the tire so it builds up along the bead of the wheel and rub it around with your hands...takes 2 minutes. Works great.
On beaters or cars I'm flipping, spray paint will do but you'll be painting them once a year to keep them looking good because spray paint and brake dust don't get along so well.