I find the best general purpose cleaner is a disposal baby wipe. There's usually a bit of alcohol in it and the wipe itself is great for scrubbing dirt and mud from wheels and tires and for scrubbing chrome parts clean. The only thing a wipe won't touch, in my experience, is old gluey grease, but you probably don't run across that in general cleaning. This is typically how I clean my bike -- I very often don't use any water. I'll often just use five or six baby wipes. They're wet enough to lift dirt away, but not so wet that it drips all over the shop floor.