Prespray with
Harvard Chemical Free rinse pro, acid rinse, boosted with 20 vol Sally's.

Then rinsed with some Fury from Harvard
Here is Big Momma my PMF 703 rinsing
The after pics
This job was recommended to get replaced, 2nd time I cleaned it. I got the ole "Just do what ya can!" I informed that I would not clean it again and she needed tile installed. Surprised it wasn't dripping downstairs from the ceiling.