Hahaha

It does look like a dead chick, but I promise it isn't as bad as it looks.
I have tried the "hanging" method. It really does work most of the time. But like anything you have to be experienced and know what you are looking for. I keep their feet on the ground, just make a loop with my fingers and stretch them out. Roosters will fight you immediately, but so will a bossy pullet. I test it multiple times as they age, sometimes you get mixed answers even back to back. It just takes trial and error until you get an eye for that too. That's how all my grandparents and great grandparents taught me, so that's a big factor I look at when sexing.
Vent sexing, I don't really like to do it personally. I just feel like I am squishing them too much, because that is one option I just don't practice enough to be efficient. But to those that can do it well, I applaud them. I would love to be able to do it like that.
I just sex mine out of curiosity, just so I have a good idea what to expect. (If I need to hatch or buy more, so I know I will end up with enough pullets) I keep them all until they are fully feathered, and I know for sure. So I am not worried about which are definitely males and females. So it's not a big deal if my guess is wrong.
With wing feather sexing, I feel like it has potential to work under the right circumstances. But I feel like it varies so much, and there is a certain time period when you have to look, I just don't really rely on that method much.
Other than the hanging method, I mostly just go by looks. I will have some hatch and are less than a day old, and I will know if they are pullets or Roos. And some I just have to wait and see.
Another option that the old feed store farmers would do, they would sometimes walk in with a piece of something tied to a string. Put it over their heads, and would sex them like that. I have always heard stories of people doing it like that back in the day. I would never be able to do it right, and wouldn't reccomend people doing it for accuracy. But no joke, once they came and picked out all the pullets, we would get complaints from all the other buyers that came after them because they ended up with all roosters. And the string farmers when we asked? ..."no problems at all, I have lots of pullets. Send them to me and I will sale them some."
I agree, I bet your dad just has an eye for it haha. I bet his guess is right.