BAT should be a dance between the dog and the person. The human is the one who knows the plan for the dance, but the dog is the one who has the understanding of rhythm. Your job is to read your dog and know when to cue him run away, or when to stand your ground so the dog can gather info. Importantly, you need to note signs of increasing arousal, so you know when to stop moving forward.
The leash is a force field, not a correction tool. Your leash is there for safety and fluttery communication to the person. It should be attached to a harness, preferably the back of a harness for set-ups (possibly the front of a harness on walks). This physical connection to your dog is a back-up for your mental connection, not a replacement. It should not be used for leash pops or sudden stops, whenever possible. slide your hand along the leash so that your dog gets the feeling of brakes being applied versus hitting a wall.
I find it helpful to use a 15 foot (5 meter) long leash for BAT. I don’t recommend much longer than that, or it just gets awkward and tangled. In a pinch, I’ll do that by clipping two leashes together (like the Halti leashes, which you can clip twice) but I prefer to have one solid leash. I use my right hand to gather up loops of the leash and my left hand to dole out or gather up the leash.
For a BAT set-up, there is a time when you stop the dog. Like I said, help your dog figure it out without the leash. Body language and brakes with the leash go a long way. As you are running/jogging/walking away in the reward phase, let out some slack in your leash so your dog can jog away at her own pace.
These longer leashes may take some practice to use on walks, but they are pretty cool. Only do so if you feel that you have control over your dog’s safety and the safety of others. Never let your dog go around a corner without you!