3. Use Floetrol
This tip is actually more for painting furniture, trim, and cabinets than walls, but it’s so good I can’t not include it. Floetrol is a liquid paint conditioner that extends the drying time of latex paint, which all but eliminates any brush marks and gives you a perfectly smooth finish. It’s fantastic. Also, it’s cheap and easy to find. It’s a must have for any DIYer.