I well remember "Big Wally", but we never bought it as my mom said it was a very expensive way to clean walls. She would usually use Tri-sodium phosphate in a bucket of hot water, sometimes with a little bit of Lux dish detergent. It was made very plain to me that you started at the bottom of the wall, and worked upwards (to avoid streaking).
This product was being advertised on TV in Summer 1972, and my cousin Kenny was almost 5 at the time. His mother (my Aunt Margaret) was from Scotland, and they would refer to a certain part of his body as "Wally". So when the ad was shown, he would remark that he had "big Wally", too. This would embarrass my aunt, but we got a big laugh out of it.