Similar scenario while we were underway. I managed to get that DC motor free and on to the cockpit floor. There were four little hard rubber covers that held the brushes in place and when I pried them open the black dust that came out was phenomenal.
I used a spray-air can (duster) and some spray electrical contact cleaner to clean it up and it worked fine for a couple of weeks until I could get it to a re-builder in St. Thomas(USVI).
One note; if you take it to a re-builder they may try to sell you a new relay. At least in my case the fellow was a skilled auto mechanic but didn't understand why the unit wouldn't work when case-grounded so he wired up a whole new automotive type solenoid. I didn't get too far trying to explain it to him, but eventually he let me take the motor back and didn't charge me for the relay. I wired the thing back up properly (take pictures!) and it's worked perfectly since then (about a year now).
sv Adagio, SM 209