I'm going to use a self leveling underlayment in my basement (Laticrete 86) and I need to prepare the floor with the primer. Currently there is some paint on the concrete that the previous owners put down. I have no idea what kind of paint. Some of it flaked off, but most of it adheres to the concrete pretty well. Is it absolutely necessary to remove this paint? What will happen if I just put down the primer on top of the paint?