It has to be BIOLOGICAL POWDER. For it to work.
If you are getting white stains everywhere your using too much!
You need to fill up your bucket with water and a small dose if bio powder. Agetate the brush in the bucket with the water dont put the powder directly on the brush, it won't work. You need the enzymes to be floating in the water and then put the water on the brush that way. If you just powder the brush all you are doing is chucking powder everywhere.
Now of course it wont remove non biological stains, chemcial stains will not come off. You need to use bleach or somethingnlike that.
But for the price of a quid, you can get good results. Trust me it does work. But you have to take each job on its own merits.