Waterproofing the interior of your basement is as easy as going to your local hardware store and purchasing a bucket of waterproofing paint. Before applying, make sure your basement walls are dry and free of any existing paint. Waterproofing paint can be applied like regular paint, with a roller or a brush, though Mar-flex recommends a brush for precision application. Make sure to cover as much of the wall surface as possible, and ensure proper ventilation while painting. Mar-flex offers sealant products to make the job even easier.