I would like more information about "bartering" as a way to earn and report income and thereby earn social security credits.

[RickInFlorida]

So you can email them, but not to ask questions.  And you can call them, but nobody ever answers the phones or return calls.  Or you can visit their local offices, but, I was told by a local rep, local reps are not trained in tax law and probably won't be able to answer questions.  They are basically there to receive payments and work out payment plans.  This is what we're up against.

[TomD8]

This is a very long shot, but back in 2012 I successfully emailed the IRS with a tax question.  I got a good, detailed answer.  Unfortunately I only have a copy of their reply, which came from the email address <a rel="nofollow" target="_blank" href="mailto:taxhelp.rmail@irs.gov">taxhelp.rmail@irs.gov</a>
I don't remember if that was the email address I used to contact them.  But if they won't reply to the email address I gave you previously, you might try this one.
There's no question that your barter income is taxable.  The only question is whether you should report it as Other Income on line 21 of your 1040, or as Business Income on Schedule C, which would generate a Schedule SE.

[SweetieJean]

https://www.irs.gov/newsroom/bartering-produces-taxable-income-and-reporting-requirements

But your first situation is more complicated because it is happening in a foreign country.

And I don't see the usher role as being a barter. Otherwise, everyone who did volunteer work of this nature would be required to claim it.