vibration collar to leash walking? I wouldn't go there, would be pretty difficult to get timing and communication down properly. plus managing a leash, a pager and treats with two hands... and remember the buzz needs to mean one clear thing to the dog (so you need to train and desentize to the collar first as well as train that command under various scenarios to proof)
There are tons of tools to help ensure you have control of the dog while you train. But to me that's all the tool does, help control to ensure they don't get loose or pull you down the road. The important part is the training you do to teach the dog what is expected (not just what is not expected).
You can train a dog without a training collar, but this works best with young dogs who haven't built up lots of reinforcement from pulling. Those often need a safe tool to ensure they don't hurt themselves or others during training.note that a flat collar can cause damage to the neck/wind pipe if a dog is pulling regularly.