As Paul c on his first cleaning advice, I would only add to work controlled sections not try and do half the floor at a time, I work in 2-3 Sqm at a time , pre wet the joints with a sponge ( this will aid to stop the acidic product lightening or burning the grout in the joint) and test the diluted residue remover product you have. Work with the pad, remove and rinse well. If you are left with a white cloudy smear after this test again or you may need to test an alkaline product to break the polymer