First, get yourself in a round pen or smaller area, to give him more distinct boundaries. This really does help.
Horses read body language more than they listen to voice or whips when you're on the ground. You need to use your body language to project what you want. Horses have a "drive line" that depending on how you position yourself, will send their energy forward or backward. The drive line is right at the horse's girth line. If you keep your body behind that point and focuse your energy on your horse's hip, he WILL go forward, and keep going forward until you "tell" him otherwise.
Say he's going clockwise, tracking right. The lunge line should be in your right hand, held at hip/waist height. Keep it off the ground. Your lunge whip should be in your left hand, pointed at his hip, with the end towards (or on) the ground. Only lift it when you need to cue him, otherwise keep it pointed at the ground. If you have a really sensetive horse, then you can point it out to the left side, or even reverse it, so it's pointing behind you.
Your body should be behind his drive line at all times, so you're parrallel with his barrel. LOOK at his barrel or hip, stand up TALL, shoulders back, look UP, and command his attention. Send your energy to his hip. Watch his feet. When he starts to slow, take a step toward his rear and flick or crack your whip behind his heels. Say whatever word or noise you make for "faster" (I say "Trot-On", "Gallup", Walk-On", or cluck/kiss, depending on what gait the horse is in and how much enouragement they need). Be sure you're still standing tall and use a low, but authoritative voice. Don't yell or get high picthed; horses have very good hearing. You could whisper and he'd still hear you
. Keep your tone even, but firm. As soon as he speeds up, take your step back to the middle, point the whip to the ground, but KEEP looking at his barrel/hip and be sure your body is still behind the drive line.
Once he understands forward (in BOTH directions) at whatever gait he perfers, THEN you can work on getting him under control. I don't like to confuse a horse that's already obviously confused, so one thing at a time,
Now that he understands to go forward when you say so, you can start fine tuning him. The best way to do this is to learn how to "half halt" from the ground. You use your body to say "hey! Look at me and chill!". Get him going nicely around your circle. Wait until he's calm and in a good rythm. (Still tracking right) Step to your right and in towards his head a half step, look at his head, keep the whip down or behind you, and say "EASY" in your calm but firm voice. Watch his legs closely, as soon as you see him "pause" step back and to the left, maintaining your "go forward" position. You don't want him to break gait, you simply want him to "think" and slow down a bit.
If he breaks gait and slows to a trot or walk, or tries to stop and turn in, don't get frustrated or mad, just send him back out. This means that he is sensitive to you and you need to use less "force". Next time, just take a step to the right, not in toward him, say "Easy", then step instantly back to where you were. Tell him "Good Boy" when he does it right, so he understands what you're looking for.
The in hand "half halt" is a powerful communication tool between you and your horse. Once you have his total understanding and respect, you can half halt your horse when he's 100 feet away 8). You might need to get his attention first though, lol.
Use the same technique to get your horse to transition down, stop, stop and turn in, or stop and roll back using varrying levels of "force". You just have to play around to find what works best for your horse. To stop and roll back, you'll need to change your whip and lunge line hands, and continue to "drive" the horse in the new direction, withough chasing him. First practice Stop & Turn In, then send him in the new direction. I use the word "turn" as the horse is turning in the new direction, so you haveone more cue to confirm what you want. Once he's doing well with that, try picking up the pace to see if you can get a stop and roll back, and then even more advanced to a straight roll back. You do NOT want to try this though until your horse is calm on the line and 100% listening to you, and you've gotten to where you know all his buttons.
Lunge line and round pen work is an excellent way to bond with your horse and fine tune his training. Once you have him going well on the ground, you'll find your undersaddle works goes even better!