I got the product from Home Depot. After degreasing the effected areas I sat down on the edge of the tub and started painting grout line with an artist's brush. It worked wonderfully!!! The only minor drawback was that the newly treated areas looked so much better than the non-stained portions (which were to be left as-is), that the project expanded about 2-fold. Overall I did everything up to about waist high at the front and long wall of the tub. The back wall was in pristine condition and I left it untouched. Thank you group!!! Great advice.