Depends on which wheels, the aftermarket Racing Sparco's have to be cleaned on the inside everytime or the job will not look finished at all. I took a 1" dowel rod and planned down flats on opposite sides of each other (to allow me to get between the calipers and wheel) then wrap a towell around it and fish it between the spokes back to the inside lip.
On the stock Mach1 wheels I use the same method but can't get the middle area behind the wide spokes. You can't see it but everytime I have the wheels off I clean that area up too.