Sally

Rider 2 (first behind the leader), marks the first junction when the leader turns off.
Lets the whole group pass until he sees TEC, and rejoins at the back.

Next junction, the orginally 3rd rider(who is now behind the leader) marks the next junction, and rejoins when he/she sees the TEC.

And so on and so on..

Saves the need for markers that need to pass the whole group to get to the front to mark again.

But thats only my 2p.