@houghton I’ve been using Movetodon: https://www.movetodon.org/

Works like this:

1. Sign into Twitter, sign into your Mastodon instance.
2. Movetodon finds your Twitter followers with Mastodon profiles in their Twitter bios.
3. Shows them all in a list, with “Follow” buttons (or “Following” for those you’re already following on Mastodon.

By default it sorts by how recently they joined Mastodon, if you have 200 today, and check again next week, the top of the list is people who just joined.