I don't know if there's a correct finger to use, but I've caught myself leaning on my machines with all my weight resting on my hands, which leads to sore arms and hands. Keep it light.

Yep. Don’t lean on the game. Stand at the game. A trick I learned was if you can take your hands off the game and not fall over then you’re doing it right.

Playing too much? I know my hands & fingers hurt after going to a pin show.

This! I'm fairly new to the hobby and after each league night I came home sore as all hell. Then I realized I was putting all my weight on my arms cuz I was leaning. It's hard to get used to as I think we have a natural tendency to lean when playing. Now I try to remain conscious to not lean when I play.

I always use a seat playing and a cup holder
No issues

Better than standing on the game. I learned my lesson the hard way last week.

If you're falling over playing pinball, something's wrong!! Playing drunk?

don't lean your weight on the lockbar, maybe put the entire macine a little higher or lower on his legs with the levelers so you have your arms in a different angle. mind the pitch!
i flip with my middle fingers btw.

Sounds like basic repetitive stress. If your not experiencing other carpal tunnel pain when typing or computing or other activity, this may have tipped it over the edge.

You can get immediate relief with wrist supports you can buy at walgreens or walmart. I've used the short ones with the insert from time to time and avoided having to have surgery. I'd wear them playing pinball and computing for a bit and see if that helps. If not get it checked out.

Sounds like your having fun be careful. Don't ignore or put of carpal tunnel pain. I've been lucky myself but know a couple people who put it off and even surgery didn't help much.

As has been pointed out, you don't want to be supporting your body by leaning on the machine. Putting your weight on it like that also makes it harder to play - you won't be able to get the nuance out of the flippers that you'll need - you will end up just hitting the flippers at full velocity every single time. Try hitting the buttons more gently, you'll notice the flippers can vary in strength the harder/faster you push the button in.