It's often said that simple things work best, in this case ... true. I always keep my car black and shiny but the dirty wheel bolt apertures has always annoyed me. I had to spray each bolt hole with Mr Muscle Kitchen Cleaner ( honestly ) it was all I had. Left them to soak and washed the rest of the car, then came back to the bolt holes. I found it a bit fiddly to get in around the bolts but being wet helped. Then twisting it back and forth a few times and clean wheels at last, after 9 years. Cheap, cheerful and works ... delivery was prompt so all good...