I have done a lot of lead-follow training over the years. Very good Power Flarm helps with the correct hardware. You need a good PF core with solid antennas and hardware such as a Oudie or LX9000 display.

Using Team Codes can be very useful. Establish the reference point between the pilots before flight. Very simple after that to give or receive exact locations between pilots. You can use a goto the other pilot and they can fly directly to your location.

As Mike said, the lead pilot has to be ready to pull the boards and join the following pilot at their altitude.