Turn Signal with Dust Issue

I have a 1981 DL sedan. Over the past year and a half, I've been having problems with dust building up on the turn signal. I suppose I should note that the problem coincided with my start of driving on a lot of gravel/dirt roads (inside of the car looks like I could grow a garden after just a couple of days of commuting).

The left turn works fine, but the right balks. I'm pretty certain it's dust on the contacts as cleaning it off with compressed air (big stuff at a garage, not the canned stuff) seemed to help for a couple of days. Have also used the contact cleaner in a can (didn't really help) and a Q-tip with rubbing alcohol (worked for a couple of days). Nothing seems to work for long. My logic is that the problem is with the right turn because the dust settles on the top which is where the contact for the right turn is--hence, I figure dust is the issue..

Wondered if anyone had a suggestion as to a preventative measure so it would function for a bit longer.

Thanks!