In reality, a new apprentice is not given a big infodump either, because they would be unable to retain most of it.
Since this is an army, they will have regulations on which information to present, in what order, and how to verify it has been understood before letting the new enlist even near anything that is more complicated to operate than a light switch.
If an army ever needs to improvise or rely on any skills they have not previously taught, things have gone sideways quite a bit already and there will be an inquiry as soon as possible.
So, the character will be given information only piecewise, and according to the same plan that their instructor was taught under:
- "do not go near device X"
- "here are the necessary safety precautions you need to understand so you can go near the device"
- "here are the necessary checklists you need to know by heart to bring the device into a safe state if you are ever not 100% sure that device X is operating as intended"
- step-by-step instructions of common tasks, with error paths ("if this gauge goes into the red, run that checklist")
Details on how it works come a lot later than that. If the instructor deviates from that "safety first" order, that is already a moment of tension, and will be recognized as such by any character who understands that this is not how things are done.
Since your character is new to this environment, they can still break that mold and simply ask questions, but the answers will be short and try to move the conversation back to the task at hand.