That's definitely true! A soft brushing and spot cleaning will do wonders for wool. Especially coats. I have a vintage 50s' cashmere coat that I've owned for over 20 years, and I've only had to have it cleaned once. Granted, I haven't worn it in several years (as I'm currently, ahem, too large for it), but I wore it as my everyday winter coat, and would simply brush it out with a very soft brush once in awhile. So, I wore it almost daily in the winter for around 12 or 13 years, had it cleaned only once, and it still looks like new! (And, by George, I'm gonna get back into it!)
Never heard specifically about using vinegar to clean it, but vinegar is great on many fabrics as a cleaner or, better yet, a component in a home-brewed cleaning solution.