For my wheels I used liquid dye, 50ml of dye to 2L warm tap water in a big icecream tub. To make the masks I used normal PVC glue, let that dry. I sat the wheels in the tub on some jar lids to let the whole wheel be exposed to the dye.
If you have new wheels they should colour better, the old wheels I used turned out all unshiny and faded.
EDIT: Luke, your wheel is gonna be a retarded colour once it comes out, just a heads up.