Among the many different microfiber brushes designed for wheels that I have bought, I have one of these that didn't work to well as designed but mine has a removeable cover so I took the cover off and use it regularly for the spokes and the inside part (barrel). For the barrel, I just sort of drag it along the inside perimeter of the wheel by hand. I also bought a bag of cheap 100% cotton gloves off Amazon and use my fingers to get to the crevices and corners that the brushes don't get. You can reuse the gloves or just throw them away since they are hard to get 100% clean after using them.
Mine are the silver 930M wheels and I likely will need to jack the car up every year or so to completely clean the inside barrels - Or, better yet, pay a detailer to do this.
