Over the years I learned that every goalkeeper trainer is different and if you are able to find a good one, hold on to him/her as long as you can.
My kid was lucky enough to have a great keeper coach when he was 11-12. He was very technical and my boy learned a lot in a very short period of time. About 4 years ago this keeper coach was offered a spot to play internationally and he left the States. I tried everyone available locally in South Orange county (didn't have an option to drive far), but could not find anyone even remotely close to what this guy was.
He still comes once in while to visit his folks and whenever he is here in Cali, my kid is still getting a session or two with him. I wish it would be more trainers like him - true professionals who care.