Try doing like I said. Do you not have an xjet? Spray it on at ratio of 4-1 and then surface clean a section and see what it does. May have to do twice but can do a DG parking lot with 5 - 10 gal. Of course HD stuff may not be as strong as what I get from chem supplier so maybe try 3-1. Don’t really need to brush it, you’re not using F9. Got to use some pressure, like 2500-3000. I deal with mud stains about 3 times/week.
Typical subdivision site around here:
