Hopping on a call with another group owner in a companion niche to yours can have amazing benefits.
You network, building strong relationships and get in front of their members, they get in front of yours. It's instant trust because the other owner is essentially vouching for you.
1. Find someone that you feel is knowledgable in their niche with a group that complements yours (if you teach fitness, find someone with a nutrition group to collaborate with).
2. Ask to do an informal 30 minute Q&A for their members on a specific topic.
3. Both of you post the link to the live in your groups.
4. Reciprocate by letting them do the same in a meeting in your group.
After the call, just mention to people where they can find more of your stuff. No hard push.