join a party in progress

Some new players in my FC asked me to come tank Brayflox story mode, cos their tank dropped out. I'm new-ish too, so I wasn't sure if I did this right, but I opened duty finder, and clicked party in progress for Bray. I ended up with a different party, not my FC mates. What's the proper protocol in that situation? Is it acceptable to leave the party and try again to get matched with the right group, and if so, how do I do that? This time I just stayed with the party because my FC mates got a tank a minute later. But I need to know for next time.

It sounds like you did it right. It's really up to you if you want to stay or leave in that case, but I think leaving might give you the 30 min wait time if you ended up completing the party by joining (someone correct me if I'm wrong).

One way to tell if you are with your friends when you queue in-progress is to be mindful of the dungeon progress. If they're past the 1st boss for example, it will say In progress: 1 / #