Thanks @Victor. Yes, I saw your video and was going to do that, but this is how I ended up doing it:
When the user is created I set a random password and save it to user: tempPassword field, then copy it to password field (two actions).
Then an action sends a sendgrid email to that user with a welcome message and the temp password.
When new user tries to login, the login submit button has two conditional actions. If tempPassword is not 0, user logs in then has to set a new password, then an action to set tempPassword field to 0. If tempPassword is 0 then do normal login.
Works quite well actually, I’m very proud of myself 