if i were you, i would do it myself, especially since he already has a little bit of a foundation. 90 percent of successful riding is done off the ground first, at least in my experience. if you have access to a roundpen, have some sessions with him doing ground work with and without a saddle. he already knows you and trusts you...just build off of it. i use clinton anderson and john lyons techniques to train my horses (with some of my own ideas thrown in) and they havent led me astray yet
first, i would make sure he knows how to free lunge and change directions with and without a line. then id practice lateral flexion and make sure he knows how to give. if he respects on the ground, and understands the saddle wont eat him, its time to hop on in a pen or arena or pasture.
i hope that helps. ive used this philisophy on all of my horses, some of which have bucked riders off, were off the racetrack, or were "broke the cowboy way" and i have had great success by just creating a respectful relationship. you just have to find what works for you and your horse on a personal level.