On wood I used a brush to apply. It was mostly to apply evenly than to actually scrub. Scrubbing was not necessary. I tested a few out of sight spots first and determined that leaving it on there more than a minute(60 seconds) and it did too good of a job (if that makes sense) I had a charged water hose handy for quick rinse. stone/cement will surely take a little longer. I would do like I did and find an out of sight test spot if that's possible to experiment with initially. Sure hope it works for you. Good Luck.
"The Poor Fish" circa 1930's: The Poor Fish wouldn't have been caught if he'd known enough to keep his fool mouth shut.