My old guy injured himself around his tail once and I had to clean it and vaseline it daily to prevent infection. He didn't like it in the least, yet he never so much as offered to kick. He dealt with it.
Even my young one, that was quite shy and nervous about having her hind end messed with I can touch all over and braid her tail no problem. I have had her a lot less than 6 years (she's 2 1/2). Even when she was still nervous about it, she never offered to kick, just moved away.
Your horse should NEVER offer to kick! What if, like with my old man, you need to tend to a wound? Will he kick you and put you in the hospital or will you back off and let the wound get infected? Hopefully you won't have to do that, but the point being, your horse should let you do what you want without so much as offering to kick. That being said, I strongly suggest you find a trainer. There might not be any big name trainers, but that doesn't mean there aren't any. I found a trainer that is willing to come to me. It's a little pricier than regular, but I have no trailer currently. Go to your tack/feed store, shows, ask around about trainers. Maybe there isn't one just around the area, but one a little further. Kicking is a very dangerous habit. He can break bones. Especially if wearing shoes. Therefore I say you need someone that knows what they're doing and his dealt with this problem successfully before to help you. For your own safety. You may be able to pm some members here that live in your area and ask them for suggestions on trainers. Good luck.