I use car wax, and to be honest haven't heard about the 'oily rag' method. The product is designed to clean and restore the sheen to dull paint, so it works well enough that I haven't needed to look for an alternative. It's a time consuming activity, but worth it for those special machines in the collection that you want to display.

Personally, I use just plain old lemon oil that is used for wood and whatnot. It was available to me, and works rather well. It will get any surface shiny for awhile, however it won't stay like that for long if you use the machine often. So it's really good for just nice show machines that you don't plan on using too often.

The car wax shine lasts. I'm not so sure about using lemon oil on paint; it's meant to restore lost oils in wood.