Yes, Sherwin Williams Pro Classic acrylic is a leveling enamel that works great on vertical and horizontal surfaces. On vertical surfaces, you have to be more careful not to apply the paint too heavy otherwise it will drip, but with just the right thickness, the enamel lays out really nice. I've painted many staircase posts and spindles with Pro Classic. It's a good product. It's a little tricky to work with at first, until you get a feel for it. The enamel starts to set up fairly fast so you have to brush it on quickly. The enamel sprays really nice too if you decide to go that route. Use oil-based primer on the posts.