I did this to find theaters where I could play in the pit when I was detailed to Sunnyvale CA for a month in 1986 or 87. Got to put two more shows under my belt, and kept my skills up while I was gone from home. And, it gave me something to do with my evenings besides eat myself to death.
I did my research via telephone, and I won't say that it was easy. However, in a large metro area like the Bay Area, there was plenty going on, to the point that I had to choose two out of three shows.
I gave up on concert bands back in the 1980's, this due to the politics and "possessiveness" of the players in same. I tried a couple back in 1992 (my town has a band, for example), just to see if my attitude had changed, but I've not darkened the door of one since.
Pit orchestras, well they're another story entirely. These days, I do three musicals a year (in the spring), and I've been known to sneak in another couple here and there when I get the chance. Private schools, churches and community groups down here pay pretty well (say $500 for six rehearsals and three or four shows), but the main thing is the challenge.