I did a Medical Centre yesterday and you need to get the crud up first before you wet it, I used my host machine and my sebo vac, then I flooded with hot pre spray and hwe, the results in some areas were astonishing and in some areas even after a few scrubs and pre spray again and again came up OK, the practice manager was delighted as she knew how much work I had put into it, I turbo dried as I went along as it makes it easier if you need to redo any areas.
But pre vac is an absolute must IMO.
Shaun