How can one develop coping mechanisms without voluntarily undergoing hardship?

There's a more fundamental problem here.

Suffering and hardships make you stronger, and teach you to cope.

But with no suffering or hardships, even if you knew how, what would make you want to get strength and ability to cope?

And I'd say this is not something that can be done on the "it would be cool if I could do that" level of motivation.

My guess is you don't make serious progress with this until you are desperate. If you aren't, even knowing the "perfect method" wouldn't help you.