Team Crossword

There isn't much to describe but I can confirm you can join daily crosswords in progress, no need to make them yourselves or complete them solo. You also do not need to do these consecutively so this will just come in time. I am unaware of any way to trick the system like you can with similar achievements on an xbox or windows phone and changing the date.

To help with this when you join a daily crossword in session, pick one that is close to being solved. That way you don't need to spend a lot of time. Or you can just start your own and finish it yourself. However you want to do this is up to you. Personally when I would fire up the game I would look for puzzles that were at least 70-80% solved. Just pop in and help finish it off. So long as you were in the crossword before it ended it should count. I started on May 18th and played each day (except one) until the 28th when I earned it so it unlocked at exactly 10 puzzles.

Also as far as I can tell there is no count in the game to tell you how many daily puzzles you've finished. It seems you have to keep track of this on your own.