for any of the projects I have worked on, from doing DIY coins for people, to the Mojo coins I assisted with, the pepeflyer coins, my pokerchip sets, the amount of coins I have keyed approaches 1700-2000

The process I use is very simple.

I use an airgapped computer that has bitcoin core and the samr7 vanitygen program installed. This system is never online. It is updated with disposable usb drives that are used to install updates and move files to the airgapped system. The usb sticks never go from the airgapped system to an online system and are disposed of after one use. This is done via my fire pit. Periodically, I also replace the harddrive in the airgapped system disposing of the old one via the same burn pit.

I use an old printer that has no wifi or bluetooth capabilities - it is a laser printer and I print on Revlar paper.

I have used text for private keys, qr codes and many times used both text and qr code.

I do not save any files to the airgapped system. Keys are printed and locked in a safe in my office. If the keys are ever out and I leave the room or they leave my sight, they are disposed of and new keys are made.

If anyone ever has an issue with my coins - it will not be because someone is sweeping them. It will be a human error on my part.

Examples:

putting the wrong key on a coin (I have done this once that I know of - customer contacted me, I reimbursed them for the load)
I once put the QR codes backwards - with the private key facing out and the address facing in, when identified, generated new key and address and re-did the coin.

No one is free from making a mistake and there is a huge difference between making a mistake and being malicious when it comes to keys.

Keys should never be saved or stored where someone else can get them.