If your computers aren't networked, it shouldn't take an hour to copy a few files to a thumb drive and move them between computers. If they are, then share your iTunes libraries between computers. A song transfers in less than ten seconds.
The problem is apples business model is to capture you within their ecosystem. Itunes is the worst part of owning an iphone especially if you have to use the PC version. I have music I want to add to my phone but it is on the wrong PC and I don't want to take an hour with itunes to add a few songs.