I want to repaint my 50 year old aluminum sided cape. To my knowledge, it's the original paint. Yes, it's white, chaulky, and dull. The siding itself is in good shape, no bare spots, dents, or peeling. Do I need to prime the house or is the power-washing enough? If I do have to prime, I would be using 100% Acrylic Latex primer, followed by 100% Acrylic Latex finish coat. Is that right? Thanks!