How to teach XC with lead/follow technique?

We are trying to help teach XC to our fellow club members. I've heard of the Lead/Follow technique with an experienced pilot showing a student how to get around a course. Before we try it, are there any suggestions on how to best do it?

I've heard that if the leader is higher up or in a higher performance glider it is good to sometimes pull the spoilers and get down to the level of the student.

Should it be a 1:1 leader/follower ratio or can you have more than 1 follower?

I suppose a good talk on how to enter/exit and thermal together is the first thing - since they may not have flown gaggles before.

A portable flarm would be good to add to the student's gliders just to be able to track them.

Chris