Don't use a "special brake cleaner" - usually those are meant for car brakes and have various toxic solvents. Try cleaning the rims and pads with alcohol. Wipe once with one rag to get the majority off, then again with a clean rag to get the rest. Take the wheel or the brake pads off to give them a thorough cleaning. If you take the pads off, try sanding their surface with some fine sandpaper. This will expose uncontaminated surface to run on the rim.

And figure out where the grease is coming from!