My preferred method of getting foreign currency is to take it out of an ATM on arrival in another country. That way — even with foreign currency transaction fees — you’re getting a bank’s rate on the transaction rather than a retail rate. And I have an ATM card that doesn’t charge me foreign transaction fees. The most popular one of those among travelers is probably Schwab.
And the way I’ve always converted leftover cash at the end of a trip is to use it to pay any hotel folio balance on my last day. Another trick is in many countries to add it to a Starbucks card. (Those two strategies, combined with a credit card that doesn’t add foreign currency transaction fees, keeps the excess cost of purchases abroad low.)
But I don’t really do either of these things anymore. I like to have cash on arrival and not have to dart for an ATM at the airport. So in any country, with any currency, that I’m likely to visit/use again I don’t turn back any excess cash before leaving. I keep Euros, Pounds, Baht, Pesos (of various nationalities), Dong, Dollars (of multiple kinds).
Because I’ll use them all and in most cases within 18-24 months.
Strictly speaking that means I’m holding excess cash (I have more foreign currency in total in the form of cash than I do US dollars) and am therefore not earning a rate of return on it. So it may not be the most efficient. But I view it as a convenience premium to have that cash when I need it, to save myself two in-country transactions.
I bring foreign currency with me on my next visit, along with no foreign currency transaction cards (Sapphire Preferred is especially desirable with no such fees and earning double points on all travel and dining which is what most of my foreign spend will be.)
What’s your foreign currency routine? How do you buy it, and do you convert it back to your home currency when you leave a country?