Housewashing process by the guy who can't burn metal

I’m too weary of the subject to explain again, but the info is here.

What 12v pump puts out 300 psi?

I pull up to the job start filling my two 100 gallon tanks of water I have a 55 gallon tank for one of my soft wash systems. I can start pretreating the area to be cleaned before the tanks are full. Then I rinse with the 8gpm pressure washer.