There are various ways to improvise a chain whip, but I have carried and used a Unior Cassette tool with good success. Whatever tools you use it helps if you do not overtighten the cassette when you install it before the trip. I once saw a guy remove a cassette with a couple pieces of webbing. It came off no muss no fuss. He said the secret was that he only tightened them a few clicks. I'd guess you could get them off if tighter, but it would be harder. His came off really easily.