It's not exactly fun, no, but it's not inaccurate either. Don't worry, I'm not going to let it make me less effective.

Obviously. I would have done something differently if you were.

Of course.

I'l let you know how talking to orcs turns out.

Supplies are same place as last time.

Okay. I'll be back hopefully soon, if all goes well.

And she's off with the supplies and the notes. Hopefully they don't turn out to be indecipherable in the classic omnidisciplinary genius way.

They have been translated from genius to something with exercises and a phrase book. Very decipherable.

Convenient. They don't need anything like fluency, and the particular sentences are probably things that the Feanorians already figured out if they tried talking to orcs. Grammar will be useful for making sure they don't misplace a "not" or forget to carry the one or something. And they can have people work it out independently, since the failure mode from swearing a false thing might be worse than simple inability to say the words.

Swearing things in languages you barely know is incredibly dangerous and several people refuse to trust the Fëanorians as far as to say words they suggest at all. Other people attempt a verification and conclude that unless Maitimo falsified all the notes specifically to hurt them this way, the ones in the phrasebook are right.

Amber would be right with them on not trusting the phrasebook if not for having more context than most. It'd definitely be plausible for the Fëanorians to want this host unable to credibly talk to orcs.

Once they've confirmed that this is in fact the oath they need, it's a relatively simple matter of finding an orc.

They grab a couple, in case the first one's not cooperative. 

So they're already surrounded by people who they'll recognize as Elves or enemies or non-orcs, whatever the category is. Well, they might not have clammed up yet.

Hello? My name's Amber. I'm willing to periodically swear that I haven't lied to you, if you'll do the same. Can you talk to me?

No response.

And if she walks into view to be visibly not an Elf? (Or Noldo, or... well, most possible categories she actually is.)

This gets curiosity and some muttering in their language.

I've heard it's only when you see the Elves that you refuse to talk, if I don't look like one it's because I'm not, is that good enough?

"I swear that I have not lied to you."

More muttering. 

Is it recognizably grammatical muttering, because no one's close to fluent but resorting to the phrase book is an available option.

They might catch a word or two. Elf. Melkor. Die. What.

"I am not an Elf," is easy enough to piece together. Hopefully they'll notice that talking needs to be done tourist style, slowly and with small words.

Some skeptical snorts, some muttering that includes the word 'Elf'.

Skepticism is all one of the things she came prepared to deal with! "I swear that I have not lied to you."

Muttering. That contains the word Elves.

Preceded by a "not," hopefully?

Can you understand me like this at all? Nod for yes, shake your head for no?

No reaction.

That's probably a "can't hear" rather than a "don't want to say."

Flipping through the phrase book translating between an unfamiliar language and a barely familiar one...
"You speak only with words, not head to head?"