you can take a kitchen garbage bag and thread it through the spokes of your rim, and then stretch it out to cover the brakes and such. Make sure the rims are real clean, also make sure you have some tire shine on the tires (makes peeling off the overspray real easy). I just did my wife's rims, and it took 4 coats of black on silver rims. Which worked out to about 4 cans. I did the entire rim though (inside and out)
It is extremely easy to do if you take the wheels off.. That's what I did.. Looks great.. We already have washed the car and no sign of peeling or anything..