Chip, Can you say why you want a super fast entry?
If you're using a sleeve, the recommendations you've recieved so far are what I would use. My only "edit" would be to Mike's recommendation of using a 30ft bungee and a line. I would skip the second line, and only use the 30ft bungee - single strand - tied to a 6 ft leash on the end.
Tie one end of the bungee to something solid. Measure out how far you can stretch the bungee and leash by walking, and when you feel solid resistance (not a huge amount), mark the ground. You don't want to mark the point where the bungee doesn't stretch any more. Also, the leash is there so you have something that's non-stretch to take your dog when you approach after the bite. Use a harness, and clip the bungee-leash on the harness.
Place the decoy depending on your specific goal. You should start with run away bites. Place the decoy within the stretch limit, and let the dog go so he bites the decoy more or less at your mark on the ground, as the decoy jogs away. Then you can work - increasing the level of "frontality" - on static bites, where you place the decoy on the mark. Then you can work "courage" test type bites, where you'd place the decoy BEYOND the mark, and you'd let go of the dog, so the dog would bite more or less when the decoy is at the mark while jogging towards you. If you do two or three reps using the bungee, and the last one without it, by simply unhitching the leash from the harness, you'll find the dog will increase his effort when he comes up close to the decoy. If the dog bites at all, this will make it so he comes in faster. He can't help it, due to the small size of his brain, but to become conditioned. :wink: :wink: Make sure you reinforce that with good takes. You won't need SUPERDECOY MAN like that. :wink:
Finally, if you focus on that your goal is to increase the speed of entry, make sure the decoy doesn't pull against the dog while on the bungee and reward by handing the sleeve during a pull, because you will teach your dog to pull away that way. The decoy should walk in to the less tension zone, after a good take...and quickly give the sleeve, while the handler is smoothly walking towards the dog, sliding the bungee through his hand, moving up to the leash. There are a huge number of variations to this, depending on what you want.