Linda, I'm not up on the latest technology, but in the past, we took some real shots: First, vaccum all possible with a good, strong back-pack vac; mist-spray a solution of clorex and a good degreaser, using a "sur-flo" electric pump and a good powerwashing-type tip/trigger gun. Even then, results aren't the greatest and we found it wasn't "salable" - - clients wouldn't guy the service. Web-search "ProCostic" and see what you get - - used to be a great painting process for tiles - ??. In the meantime, lean how and I'll give you hundreds of KFC stores to do.