Well, the main error was in not holding contact all along.
Now when you do so he doesn't understand why you're "getting in his face" so of course he objects and fusses and will continue to do so until he gets used to this new way of driving and learns the benefits of it. It's like the difference between riding western and English- a western horse is used to holding their speed by themselves once told to trot or canter and only changes when give another command. Riding them is like flipping a series of switches on and off. An English horse is collected and held in a frame by active rein contact and every little tiny change in the reins means a change in their behavior. Riding an English horse is like using the accelerator on a car. You have to hold it down and any easing of the pressure means a corresponding change in speed. What you're trying to do is change your guy from a western-style driving horse to an English-style one. It's not easy!
The trick is to teach him that the bit is his friend and that you're not getting in his face so much as offering to hold his hand. Good contact should be like holding your child's hand- friendly, open, enjoyable physical contact by which you guide each other and share information. Nobody gets pushed or pulled around and it isn't about constantly controlling every little movement. It's just about taking a feel of each other and sharing information nonverbally.
To start with, make sure your bit is comfortable for him. Can you post a picture of it for us? Many times you'll find that what seems at first like a perfectly fine bit is actually poorly made and we want to make sure your horse doesn't have a reason besides annoyance for opening his mouth when you take up the reins. Once you're sure your bit is fine, then you need to take up a more active style of driving. He isn't going to like this at first! If you have anyone who could give you lessons in person it would be good as there's a lot of "feel" involved and that can be very hard to learn over the internet.
If you do have to try it yourself without help, this is how I'd do it. You're going to want to coax and wheedle him into it; don't just suddenly take up a lot of heavy contact and expect him to get used to it. He'll probably be very confused and try a lot of things like stopping or even backing up as he attempts to figure out what you want. Stay soft and don't escalate but insist gently that he moves forward into your very light contact and as soon as he does, soften your pressure. Don't throw the reins away but let him feel a definite release so he knows he did the right thing and gets a reward he understands. Praise, praise, praise! Repeat this through several whoa/walk/whoa transitions until he gets through the stubborn confusion stage and starts thinking very hard about it. Then relax a little and let him do some long trotting with you holding very light contact and not asking for much. Put him away for the day and let him think about it.
The next time you drive, take up that light, elastic contact right from the beginning and start building on what he's already learned. Start asking for turns and holding contact for longer and longer before, during and after the turn cue. Get him thinking and moving and listening to your hands without resenting them. Start throwing in some gait transitions with contact as well. This is going to be hard work for him! He's not used to carrying himself in a frame as you're asking him to and he's going to tire quickly. Keep your sessions short and do different things like jumping or in-hand obstacle work on alternate days so he doesn't get frustrated.
Remember that you don't want to make him feel as if you're asking him to move forward into a hard wall. Your contact is going to follow his mouth as he moves his head around, remaining constant and soft. You're just going to put it out there and wait while he tries various things- when he gives to it and moves forward, he gets an instant release to tell him he did the right thing. A release in this case is not dumping your contact, it's more like if he gives you two notches then you give him back one. You soften the quality of your contact, not throw it away, and then you take it up again and guide him. Be consistent, patient and kind! It's hard for a horse who's used to doing things one way to suddenly switch to another method but I think you'll both find it beneficial if you plan to show. I've helped quite a few people and horses make this switch and the first few lessons are always the hardest.
Leia
