Personally, I don't scrub hard - just firmly. But for really dirty vintage vinyl, scrubbing isn't the thing. The right fluid is. In my experience, there are two that really, really work well with vintage records - Nitty Gritty Pure 2 and Disc Doctor (which needs to be dluted). In most cases of truly dirty vinyl, where there are no obvious scratches, I find that one fluid won't do it alone, and one pass won't do it either.