I'll just chime in here with two different experiences with e-collars...
Note - while I don't like them personally, I understand and see the place for them. Neither do I have judgement about your use of them, nor am I trying to accuse you of any wrongdoing/abuse. I do just feel compelled to share one story for anyone who is less capable and considering them as an option, only to establish that in unpracticed hands they can be pretty horrible for dogs.
Our neighbours over the road got the sweetest little huntaway puppy. Huntaways are farm dogs, they're used for herding sheep through a combination of rounding up and barking. They are bred to bark. One day, the neighbours had enough. Instead of training the dog when to bark and giving him the opportunity to meet his ingrained needs (like every farmer that has a huntaway in the entirety of the country), they decided to get a bark collar. Every time the dog barked he'd get zapped. It didn't take long before the poor thing stopped eating and got terribly emaciated, and it took quite a bit longer before they finally put two and two together to realise they were causing their dog to starve itself and he became #neuroticAF. Thankfully they don't live over the road anymore - they largely got driven out of the community after ostracising themselves through their dysfunctional behaviours. I understand a bark collar is different than a correction collar, but I also understand that corrections that are inappropriately doled out can have impacts we aren't intending, and the few cases I've witnessed with more extreme unintended consequences were people with e-collars of some kind.
That out of the way, for other people looking to go the same route you have... I have also taken my dog to a kiwi aversion course that used an e-collar to correct her. There are a few tramps you can do here that allow you to take your dog off lead, but only if they've done said course. I was also applying for a job with a private conservation trust I thought I might be able to convince to let me bring my dog to work if she were properly aversion trained.
It was only about half an hour, and most of that was filling in paperwork and having a chat to the people administering the course. I took her to a public park that had a bush trek in it. In the bush, they'd set up four or five stations with either taxidermied kiwis, some feathers and scat, or some bedding, each station was a couple of minutes walk from the last and were set up where the dog had to walk near them. She was on a lead. The second she showed any curiosity to a station they zapped her.
The first one obviously surprised/scared her. She'd been zapped before, but only when she met an electric fence for the first time, so she seemingly had no context for understanding what happened. At the second one she was still unclear about the whole ordeal and a bit curious so she got zapped again. After the third zap though, she'd pieced it together - if you smell kiwi you better just pretend that oh-no-you-actually-didn't.
The procedure is to take her to aversion training once a year to maintain certification. But I reckon if that's they way they do it to protect our national bird, it's at least a good start for people looking to protect their backyard flock.
