Hi Steve, that’s a good question. My chorus has been singing through repertoire we already know to keep it fresh, touching each song at least once a month. We’ve been singing with recordings of ourselves when possible, or with learning tracks when it’s not.
As for learning music, we learned a song last month where we released a section at a time. At rehearsal we’d do sectionals in breakout rooms on Zoom where section leaders would identify possible trouble spots, give tips, ask people to sing small sections, and have the chorus sing on mute with the part-dominant learning track or with a section leader.
It was difficult to track how well learned the music was since we can’t hear everybody all at once. I would highly recommend that you have some performance (virtual or otherwise) planned after the music is learned so that people have a goal to work towards. Our new song got a lot less exciting once we’d released the entire thing because we didn’t have the ability to work the song.
Of course this is a volunteer community choir and things may be different for you.