So if I add 50% to your totals for brushing then I would need around 30 ounces or roughly a quart?
TSP is a heavy duty detergent used by painters for stripping and surface prep. It cleans and degreases/dewaxes/deglazes a surface for best paint adherence. Spic'n Span used to be mostly TSP- not sure now. Up until it was outlawed in the '70s for environmental reasons, most laundry detergents had TSPs. I use it for just about everything I expect to paint. Buy it at any hardware or home store.