Back in Australia, we used to use this method, but as Trevor mentions, we had a spinner with extraction build in, run from a van mount carpet cleaning machine. Was the dogs for jobs like that. We used it on everything from sandstone, to limestome inside and out. we had a handheld spinner for walls, worked a treat.
Its quick too, we were doing hundreds of m2 per day and if you wind up the heat, it dries very quick and can be sealed quicker.