I am going to be new to hunting too this season. Thanks for asking these questions...I am learning alot
I showed my interest in Foxhunting on FOL and my hunt has really responded..I have gotten emails and invites. Everyone has been very helpful and nice. Your hunt's secretary may be able to help you find a mentor.
Good luck and have fun---I know I will
Road work , road work, road work. Hunters need to be road safe anyway, so no reason not to get out on your local back roads and then do tons of trot sets, a little canter. Work on hard surfaces helps build bone density, strength in the hoof and makes strong, tight tendons and ligaments. You need to go about it in a smart way of course, but using roads (or hard ground, I'm on clay, so our paths get so hard in the summer they are like doing road work) you make your horse strong and tight, so that when you get into a mucky mess, they are less likely to get hurt or damage soft tissue. Nothing wrong with riding right on pavement, once your horse has worked up to it a bit and is shod, or unshod, accordingly.
Once they are legged up a bit, take them into the fields. If your horse hunted in Ireland, then he is no stranger to uneven footing, so its going to be getting YOU used to crossing rough terrain more than anything. Just remember that the horse knows best, more often than not, and let him pick which way and where he wants to put his feet. I figure that as long as we are headed in the correct general direction, the horse has every right to pick his own way through tocky river crossings, down steep hills or through rough scrub. He's earned my trust and after all, my life is in my hands. If I can't trust him to place his feet, how will I trust him to bring me safely home?
Our horses never get footsore, but I do have one that I would consider using pads for since he does have slightly thinner soles. Best is to not fix what isn't broken. If you find your horse touchy on gravel, talk to your farrier and put pads on, otherwise, leave him alone and get to work! But do make sure your farrier has some experience with hunters. A good farrier is worth their weight in gold, and is your best line of defense in lower leg and hoof soundness. I ask mine for advice all the time, he suggests different fitness ideas, feed, etc etc.
Don't be afraid to go out a little unfit, and just pull out early. Talk to the Masters when you get there, or any all-knowing members, and ask who often turns back early. Especially early in the season, lots of people will retire, or those with kids, etc etc so just ask ahead of time, then spread the word that you will likely be looking to head in early, and would love company. Always works for me!
And I agree with what a few others have said, that better to go out with a horse that is a little underfit and retire early, than one thats overfit. I make a point of keeping the green horses fit enough for about 1.5 hours of hard hunting, or 2.5 hours if its a slow day, then always pull out. No need to exhaust them, and its safer than a green hunt horse who is raring to go and no idea whats going on!