Personally, I don't hack the young ones until they've done a bit of schooling - if you haven't taught them the basics then you can't use them to get out of trouble on a hack. Anyway, basic stuff for wobbly youngsters that I go through:
1. Let them learn to carry themselves. This doesn't mean lean on the rein, it means a nice length of neck without being rude, and let them sort out difficulties. They will stumble, wobble whatever - you've got to have the balance to stick on them without yanking them around in the gob / kicking them etc. They need their head and neck to learn to rebalance with someone on board
2. Learn to be in front of the leg, and to move shoulders away from leg pressure. Everything develops from this. I call it 'cowboy riding', as we usually teach it with reins in one hand so you've got a spare hand to grab the saddle / martingale strap / clump of mane if horse stumbles and you need stability. The idea is horse goes where you say, when you say it. Most pick this up very quickly, but you will of course have some arguments along the way. Keep a sense of humor, one of those goes a long way and the horses really do pick up on your generally way of going (i.e. "He he he wouldn't it be fun to spin round and go over here oh dear a little stumble what a shame you OK? Off we go again", rather than "Get over there NOW, FASTER, Don't trip!!")
3. Make sure step 2 doesn't shorten the natural paces - you've got to let them just do their own thing and stride on (without pacing) between the 'go here do that' riding
4. When the basics are there, start turns on the forehand, then when they're progressing start leg-yielding, teaching it along the wall to start. When that's getting there, start doing all of that in true flexion and counter-flexion. This builds suppleness and the horses's knowledge that he can move anywhere with his neck where you want it. The observant will have noticed that this all adds up to the basics of all the lateral exercises: leg yield, shoulder in, half-pass, travers and renvers. You can start doing these gently (in walk) when everything else is progressing well.
5. Don't forget to jump them occasionally on the lunge (Maybe once a fortnight); really frees up their shoulders and teaches them self-confidence. The odd small jump with jockey won't do any harm - they need to know they can jump with rider - but the aim isn't height, speed or whatever, just confidence.
It all develops into a system, and you find you warm up any horse the same way, they soon know what's happening (i.e. I run any horse I ride through response to the leg, shoulder-mobilising, then turn on the forehand, then leg-yield) - This gets all bits of the horse moving.
I'll stop now, I'm rambling, but that's the basics of what I do with the youngsters.
Guess I'm going to have to bite the bullet and get him on that road!! I am very lucky in that I do have a small, quite, good rider that will get on him while I wallk along with him. 
