I experimented with this a little bit while trying to find a handgun my arthritic mother could use. Her case is fairly severe, much worse and she probably couldn't use a handgun hardly at all.
The first thing everyone will tell you is get a lighter spring, but that's probably a non solution. Doing so may impact the reliability of the gun, and it changes felt recoil which is not something such a person needs.
She had better luck manipulating more substantial slides because it was easier to grab onto. The problem was that while she had more luck moving it, these guns tended to be too large for her.
Putting the gun between your knees and then pulling back on the slide with both hands helps somewhat.
But after trying it every way we could on a variety of firearms, she was just sick of it and told me it was not worth it to her. Eventually I wound up giving her my Colt Agent, because not only can she manipulate the controls without any assistance, the trigger on it is very good which really helps her out, and the short alloy frame cuts out a lot of weight but it's not feather light like the Scandium guns. A steel gun of that size is just out of the question, so alloy or aluminum seemed the best compromise.
But she's not a gun person. Your friend sounds like a gun person, maybe he's more determined. Maybe a 1911 with a USGI rod? You can safely press check it that way by hooking your finger around the trigger guard and pressing the bushing with your thumb, maybe you could learn to chamber it that way.