where are you at?
The best instructors are an elite few. I would put BlackJack on that list not only for pool skills but teaching skills. CJ I simply don't know about his teaching so I can't say, not intended to discourage working with him, I don't know. Joe Villalpando, absolutely as good as they come! Joe Tucker, excellent judging by his video's. Jerry B, one of the first pool instructors, certainly one of the best too. Several more here on the forum, and a bunch more out there now. Been away from the forum awhile and last names aren't coming to mind at the moment.
Where you are located and your skill level would help people advise you. Most long distance instruction is of limited value although I did get a thousand for a fifteen minute phone call coaching something else awhile back, very inexpensive for value received!
I would select someone I could spend a day with once a month with intensive phone support at a bare minimum but two to four times a month would be far better. A good advisor available for in person instruction and coaching is more valuable than a great one that you can't see regularly. I think BlackJack did offer video analysis at one time. If he still does and a local instructor you mesh with isn't available then that could be an excellent start.
Some instructors are easier to work with than others. From phone calls I think Joe V and BlackJack would be fantastic, Scott Lee and Randy G both good guys and strong possibilities. Jerry B I think is great by all secondhand reports. Stan Shuffett also gets very high marks from everyone that sees him I believe. An instructor you click with is more important than having the very best if you aren't comfortable with them and don't have good communication.
When you do pick a coach/instructor stay with them until or unless you have strong reason to leave. Don't change instructors or equipment often, this includes type of tip, and don't try to get information from fourteen sources at once. There are many paths to success but taking a little from here and a little from there is least likely to get you to your goals.
Some of the top players are great coaches/instructors, some are lousy. Can't recommend any first hand but judging by his video I would try John Schmidt if he was close by and his prices inline with other instructors. I wouldn't pay a premium for a person's success on a pool table without an excellent track record teaching too, a lot of intangibles that can not be taught or can only be partially taught go into making a champion. No sense paying for something you can't buy!
Hu