I have a fairly early gig tonight which means there's no time to hit the music store. I always bring two guitars. I just changed the strings on my #1 and then checked my #2 guitar and it has pretty ratty strings from an outdoor gig we did a couple weekends ago. But I'm out of strings! What's your best suggestion for cleaning the strings on my #2 well enough to get me through tonight? Hopefully I won't even need to use the guitar - I usually don't - but I'd like to have the strings cleaned up as well as I can in case I do. So I don't have any of the commercial string cleaning products. I have isopropyl alcohol, WD40, and maybe some naptha somewhere. Which should I use?