Getting in Shape for Eventing? (horse)

I just bought a haflinger gelding as my new eventing horse. He is 15.1-15.2 hands and I have seen him jump 3ft without a problem. He is 9 and for the last year or so has only been used once ish a week and when he was used probably most of the time he was jumped. For jumping, you point him at the jump, he never gives it a 2nd look and just takes you over it. I want to start showing him in CT in Feb ish and start mini events in May. What is a good conditioning program for him? We also ride western.

Trot sets, preferably over easy hills. If you don't have hills, that's fine too, but it'll take a little longer to get him fit.

Starting off, especially with a pony that's a bit out of work. I would do two 8 minute sets. It would be something similar to this: 8 minutes trot - 3 minutes walk - 8 minutes trot. After that, I would take him into a ring and do a little bit of flat work. As he gets more in shape you can work up to two 15 minute sets and that would be all he would have to do for the day. Incorporate a lot of transitions and CORRECT lateral work into his training as well. If he's as bold of a jumper as you say I'd keep the jumping to a minimum of once a week for now, until he gets into better shape.

Trot sets and hills are probably some of the best conditioning exercises. The second the ground is dry enough to do feildwork we get our show horses out to work on the hills. My vet said walking the hills is better for building hindquarters as well, it sets them against themself more since theres less momentum

Do a lot of trotting, it's really good for building endurance. Trot up and down hills if you have them.

I would just try to ride him more often if you can or have some1 come and ride him for you

I've heard many people say to trot down hills, but I've always been too scared. How do you go about that?

Get him confident walking down hill, then start slowly trotting down. If you have a slight slope I would start there. It is important to give him his head to he can put it down to balance. If you want you can bridge your reins over his neck and sit up tall.

Try trot sets, walk/trot up hill and also try downhill while still being under you and not strung out. You could try road hacks at the walk only! It will strengthen his tendons which will be perfect for xc. (:

I gallop my horse around the area after each lesson. When he does it with ease I add a long side. My barn is in a state park so I go out on the rolling hills as much as possible.