Having worked my way through wheel acids, wheel alkalis, wheel paste, washing up liquid etc. came accross a useful solution.
Try Jif with bleach (you know the one, green plastic bottle £1.35 a go). I kid you not.
Firstly, its a cream and you can use a brush to apply. Works best if you dilute with water and mix ne to one.
Secondly, its not too corrosive. Being for use in the house itz gotta be safe to get in your eyes without too much lasting damage. If you can get it on your hands then surey it can't damage your disks, callipers etc.
Thirdly, it is water soluble along with its grimey contents so it washes off the brake dust and doesn't deposit it on your drive.

Works a treat on gold 16"s. Haven't found anything better yet. For the price you can splash out on a whole bottle per wash if you really want.

Make sure you rinse well otherwise you end up with a white residue.
End of housekeeping lessons.

 

I find getting my girlfriend to wash them the hard way is much more satisfying.