No I have not tried this how would you do that? What do you do when he drops the ballE collars (or shock collars) can be wonderful tools if used properly. I learned from a trainer, and I am glad that I did because it's not an easy thing of master. And there is a lot of misinformation about them. My neighbours were quite surprised when I explained how they work, because they did not realize that it was this complicated. They thought you just put them on and are good to go. This is not the case.
I have one and I use it. I have a reactive ACD/beagle who fixates on other dogs. But I do not use the e collar to correct him because he may think the pain is coming from the other dog. This could lead to dog fight and/or reactivity in my dog. While some individuals I am sure use them to "snap the dog out of it", that is not their best use esp in the situation you describe.
At 8 months, your puppy has a lot of growing to do and may at some point soon (8 - 12 months) enter a second fear period. You may make this issue worse.
Have you tried rewarding with a ball during walks? Or making the dog carry a ball while he's walking? These are things that have helped me and are better solutions IMHO.