Using plungers is the preferred method of the only pool company that was helpful. They also said don't drain the pool. I was not sure what they meant, but now would try the plunger method first without emptying any of the water.

The more expensive toilet plunger with the thin flange in the middle to get down in the toilet basin kept popping off and took a ton of exertion. The trick is to get a good suction then gently lift up on the liner. Then, slide the plunger toward the wall taking the liner with it. it's a bit of a trick to learn, but after an hour was wishing I had tried the plunger method first.

Caution!
Sliding the plunger along the vinyl could easily rip an older liner. Also, by pulling the liner wrinkle toward the wall, secondary wrinkles appear that can take a life of their own, but can also be worked out with patience. Just follow a path toward the walls of the shallow end and perpendicular to the wrinkle.