I would recommend ground training. I would watch some episodes on Clinton Anderson (down under horsemanship) to pick up on a few tips to gain respect and trust from your guy. I have a tb who is 17 and off the track and he can get a little side tracked. I had him since he was 5 and have gone through so many different training methods including different bits, extra lessons and other people riding him. Once I watched he’d Clinton Anderson and got my horse to move his feet and make him think, I would get much better results and he would listen to me 100%. I tried the smartpak ultracalm but it didn’t seem to help. As far as keeping him thinuking (while riding him) do bending halts (where you eould bend his head to your knee to stop him from bolting)if he tries to run away with you. Clinton Anderson has a good video on it. Also I do alot of circles big and small in the corners and if he’s bad about it I make him do it again and make sure he engages his hind quarters to really work and not be lazy. Hope this helps.