Explain what needs to be explained when it needs to be explained... Do it with action...
For instance, maybe the weapon is battery operated, then have the battery run out at the exact wrong situation to cause drama. No need to explain the battery handling during some briefing.
If you can't come up with a dramatic situation that causes problems for your character, you should likely skip the exposition.
There are basically two separate things I keep track of when dealing with exposition:
- Reader experience
- Reader understanding
Too much exposition, especially where it's not needed will degrade the reader's experience in the shape of low tempo, urge to skim or even drop the book, etc.
Too little exposition, on the other hand, risks confusing the reader (also a reason for them to give up).
There is a delicate balance between the two that may possibly only be achieved using beta readers. Unless you're really good at objectivity...
I have a rule of thumb for exposition:
Only include exposition if the information is vital to explain what is happening just as it is happening.
You can always go back and add foreshadowings if they are needed later. If the exposition introduces problems for the character, readers will usually accept them without foreshadowings.
Also, don't be afraid to confuse beta readers. I find it easier to add text than to remove it... it's also easier for a beta reader to understand and explain what they're lacking when you're too light on exposition.
Even required exposition (like anything else in a book) should have energy (dramatic, suspenseful, comedic, etc), so try to combine exposition with something that will have your reader on edge.
If that isn't possible, most authors (and their editors?) seem to prefer a short lecture instead of a confused reader.