Im not sure what the gentle walker is, but if it is any type of head halter please do not correct your dog with it on. I'm surprised that I never see any warnings on the packages but you can do alot of serious damage to the neck/ spine by jerking around their head with it on.
Either way I wouldnt recommend correcting him when he pulls to see other dog's/ people. As you've already noticed it's not working very well and inadvertingtly you will start to change his mind about people/ dogs on walks.
While you see it is as:
People appear- dog pulls- correct dog to make him stop pulling
Your dog will start to associate:
People appear-pain begins
We know through studies conducted that this type of classical conditioning can change emotional responses to certain stimuli (in this case people/ dogs who appear on walks).
You mentioned you are beginning clicker training with your buddy. I know you mentioned problems with him being startled by the clicker sound so whether you decide to use a whistle or a verbal marker do know that you can use this type of training to help your buddy remain calm in these situations.
Some things to try when people are not around:
-Ask your buddy to sit, mark and reward
-Ask your buddy for attention, mark and reward
-Ask your buddy to touch your hand, mark and reward
These become little tools you can ask for when other dog's/ people appear on walks.
However, for me personally I find that the "Look at that game" from Control Unleashed (A book written by Leslie McDevit).
To play the look at that game mark your pup the second he/she notices people have appeared.
This will only work if the people are not invading your pup's comfort zone. If they are too close he/she will become overaroused and no longer be in a state calm enough to learn anything.
This game can be played in combination with asking your dog to preform some of his loose leash walking tools. I have used it with phenominal results the theory behind the game is that if we could break down, piece-by-piece, the cycle which occurs when a dog sees another person or dog on a walk, it would look something like this:
Look-Stare-Bark-Pull
By marking our dogs at look we interupt this cycle. Of course this only works with a dog that understand the marker signal is a promise of good things to come. It sounds like you are already understand how to condition a marker signal, but you may need to try something other than a clicker if the sound scares your dog.
Keep us posted
Kayla