I wipe the chain clean and relube whenever I notice it's real dirty, hear any noise, after a wet ride or every week or so with an old t-shirt or sock. About every 2 months/1000 miles I will pull the chain (SRAM power links are great) drop in an old 2 liter soda bottle, shake it up and let is soak for awhile. Fish out with an old spoke, dry and relube. I know one guy who keeps two chains in rotation; one soaking one on the bike to reduce the cleaning time and swaps out like every 2 weeks (again power links kick a$$) Buy one of those little go/no go $10 chain checkers and check when cleaning and your cassette will last a long time; mine has 12,000 on it.

I've used Brake cleaner on the cassette, and it does quickly get rid of grease, but I worry about the impact on the wheel bearings. I just rebuilt mine cause they were grinding. Try getting some cotton 1/4" rope at the hardware, cut off a few feet and floss the cassette

Jockey pulleys I disassemble, clean and pack with auto wheel bearing grease.

A full sized fender works wonders at keeping your drive train clean in wet/gunk conditions too