The best way to do it (if you can) is to get paid for making the change.

First, study C and/or Rust on your own. Maybe do a personal project or two.

Second, find something at work where Rust or C would bring some benefits. Tell your boss that you think this would work better in a language like Rust or C, and explain why. Volunteer to try to do it. (Note: Appearing too eager at this point might be a mistake.)

Do the second step a few times and you become the Rust/C expert. And you get paid as you do the work that helps you get better!

Also know your boss. I know I cannot suggest such a thing to my boss. Generally, the more "serious" your company is with an established stack the less likely you're going to get a green light to do anything not blessed by management.

If OP plays it wrong they can also look like a tonedeaf dunce. Definitely try to read the room.

Thanks so much for your advice! I agree, having the opportunity to use the language as part of your daily-work helps massively, and is one of the best but most difficult options to realize. I'm aware this will come with some sacrifices (pay reduction, longer hours to catch-up) which I'm willing to make while I become more competent.

As for the second point, that is a great suggestion. However, I'm very limited by my current working environment (regulation, corp. restrictions, etc.) so it becomes a little more difficult.

I believe I will just have to push very hard for option one and continue to study areas of interest in my spare time. I'm reading xv6: a simple, Unix-like teaching operating system which is helping me grasp some practical applications using C.