Have you checked out the Microfiber Madness Incredibrush flat?
I have seen this before when deciding if I needed that brush but Nah, I force a microfiber towel in with my digits, but I don't have those nightmare wheels.
Calipers and 18" wheels but still tight on E84.
In the video he makes it work on the 666s.
I just use an EZ detail brush large for drum work, behind the spokes and rotor hat.
I put a new coat of CQUK3 every 6 months on wheels swap and use Akebono pads so I really dont have to try to hard cleaning my 7 split spoke wheels