If you regularly collaborate with the same accounts, you can create a group to quickly add everyone to shared channels.
To create a group, start with a channel you'd like to share. Find the Collaborators tab at the top center of the channel page and click New group beneath it.
Enter a name and description for your group.
Search by name to invite members to your group. You can add as many accounts as you want.
Once your group is created, you can make the group a collaborator on any channel where you have access. Just click add collaborators at the top of a channel page and search for the group name.