Actually WD40 - applied to the rag, not the wheels, is a good way to get dirty, greasy marks off. However, after doing that I would use a soap and water solution (a bit of washing up liquid, a Tide or OMO type paste - which on a toothbrush makes a great chain cleaner) etc. to clean them as well.
Alternatively and a lot more expensively, this stuff
is great - but like WD40 keep it off the brakes.
I use it and even though it costs more, I much prefer it over Muc-Off which is recommended by many folk. I find that if you leave that on too long, it marks the ally, the paint etc. and you are left feeling that you might as well have used caustic soda.
Try and buy from Hein Gericke when they have one of their frequent sales/discount weekends, the savings are usually worthwhile.
It's never too late to have a happy childhood!