Clement wrote a positioning guide for Udyr based on 我是TOO’s (I am TOO) video. It includes how to (1) access backline (2) counter Udyr (3) counter the counter!

Basics: You want to solo tank your Udyr on the opposite side of your main tank line. Once Udyr dives to the back and revives he will drop aggro. This causes the enemy backline to walk up and their tank to leave, giving your revived Udyr free access to backline units.

If you flip the positioning as follows, not only will Udyr charge through Shen, but he will grab the Senna in the corner.

Sylas can ruin Udyr’s positioning because he has a lower mana cost (Sylas 40, Udyr 60) and will usually cast first and charge past the Udyr. To circumvent this, put a mana item on Udyr to make him cast before Sylas.

BUG ALERT : There is currently a bug that’s linked to CC (crowd control) immunity. If Udyr tries to pick up a unit that’s CC immune (e.g., Yone with QSS), Udyr will still be able to pick up the unit and club the rest of the team with said unit.
All information is from TOO’s YouTube video.

Link to Clement’s original post