Eliara wouldn't know the specifics, but she can sort of understand enough to make sure something is running as it theoretically should.

Odgerel is likely more of a natural. She doesn't claim to know much, but having grown around her tinkerer of a brother and having worked alongside the Goblins of Idyllshire as of late means that she's able to pilot certain things fine.

Bryre does the whole "I'M AN ALCHEMIST, NOT AN ENGINEER" at the thought of touching anything machina, war or otherwise.