Removing lubricant from the rear brake and rim?
Clean them.  I'd avoid using any sort of solvent, as it would be bad for the pads and might simply make things worse.

First undo the noodle so you can access the face of the pads, then wipe pads and rims thoroughly.  Scrub pads and rims with a dab of detergent on a rag, then hose down to remove the detergent.  Reattach noodle.  (I always forget that part.)

The brakes will likely still be a bit "slippery", but riding with the brakes partially engaged for a minute or two should bring things back to normal.