30 year old house has a large double garage. Currently with concrete floor and bare brick inside. Its very dusty and I would like to paint the floor and Walls but not sure how much prep work I need to do. The floor can be dampened and swept easily but the walls are very dusty and the point seems to loosen and brush off creating more dust. Can I go straight for a specific masonry paint or do I need to prepare both floor and walls? If so what do I use?