First, use this 'opportunity' to start a Circuit Panel Layout Sheet. You know - Whenever you turn off a breaker for 'something', label/number the breaker and WRITE DOWN which switches/outlets/whatever is 'turned off' when a particular breaker is turned off. Tape this Sheet to the Breaker Panel for future reference. AND, find a 'spot' to keep a pencil (NOT a pen) on top of, or next to, the Panel so you have one handy when you need it. A small pen light (that has a magnetic strip on it) is good to leave there too.
Now, you have a couple of choices. 1) You can buy one of those Circuit Finders at your local Home Center. (If you have the old-fashioned fuses, I'm not sure this tool will work w/it.) They work great with pole-breakers. Hopefully, there's an outlet on the switch in question because you'll need one to use this tool. I'll spare you the details on how to use the tool (because the directions come w/it), BUT, I will say to be sure you 'test' the unit out on an outlet that goes with a KNOWN breaker so you get the 'feel' of how it works.
2) IF there's no outlet on this 'run' (where you might have an over-head light ONLY on the run, or something, I don't know any other way to FIND the matching breaker other than switching the breakers off, one at a time.
Oh, with the Circuit Finder, it's a one-person job. (You don't need a 2nd person unless you're left with Plan #2.) Maybe others have some thoughts. My best to ya and hope this helps.
Jay J -Moderator
PS: I voted this tool to be my Tool Of The Year. I no longer have to 'yell' at/to my wife when trying to find a breaker. Oh, I have, over the course of this past year, labeled my breakers for the entire house. It's a REAL nice-to-have!