A few times, mainly with light plates and plastic alarms, I have removed all the electrical components from the alarm devices, leaving an empty shell. Then I would take them to the sink and wash them out completely, sometimes scrubbing out crap with a toothbrush. I have also used those things called “Soap Pads” before to remove wall paint from the plastic, it works very well and doesn’t damage the plastic. I’ve also used rubbing alcohol to clean stuff off alarms. Both my 7002Ts had some sort of tan dust that was stuck to them, which I cleaned off with rubbing alcohol, and now the alarms look brand new.