Even with good paint, the paint store sales team, and the "I can do this I've done it before" attitude you can still have problems. Case in point: front doors to fancy a home in Lakewood Ranch. Coating after coating of Urethane and/or other paints, of course, cause a build up, besides one difference in product base or old stuff from the garage can lead to adhesion problems. These add up to labor-intensive stripping and starting over. Just beware!