1)Teach it voice commands on the lunge then add a rider on the lunge then try off the lunge.
2)Ride out in company, with a lead and practise out hacking. Then also have a lead in the school. Progress to doing it on own
For both you need to make sure the pony can bend and balance both ways. Many lead reins are stiffer bending to the right because of their heads being held left alot
