Hypo is the go to for us. You should get that in any farm supplies stores . The one we started using lately is brand name " red label". I can send a photo if you want.
We also use a biocide sometimes on some surfaces which can work extremely well also. We get this from Benz softwash in Co. Cork in Ireland but there are many alternatives which I'm sure do the same or similar things.
I think test patches before you do the job key for checking performance of different options. Good for you and good for customer.