How do you position your hand to use the command key? What finger do you use? Sorry in advance about what seems like a trivial question.  However, I've recently switched from PC to Mac, and while I'm really happy about the switch, this is one of the few issues I'm struggling with.

On a PC, the most important shortcuts are CTRL-A (select all), CTRL-C (copy), and CTRL-V (paste). Almost all the other important shortcuts also use the CTRL key.

On the PC keyboard, the CTRL key is in the bottom left corner of the keyboard. So, it's very easy to hold it with your pinky, while keeping your hand in its normal position, so you can easily press the other key required for the shortcut (e.g., A, C, V, etc).

On a Mac, the "equivalent" key to CTRL is Command. However, I can't easily reach that key with any finger - especially without moving my hand from its normal position - so, I can't easily press Command-C or Command-V without really focusing on it.

Is this just a result of years of practicing on a PC? What finger do Mac users use to click the command key when executing a shortcut?
You can use either thumb to hold down a ⌘ key and then use another finger to access the other key. You just have to get used to sliding either thumb a little to the left or to the right of the space bar.

Yes, this is just a result of years of using a PC.