I found that if I use Eric Daugherty's itunes export I the music I want from itunes to a usb drive. Now all of my music is drm free so I make a playlist in itunes then use "itunes export" export only those songs. The cool thing it can be configured to save you songs in multiple folders like artist -> album -> aac file. I then found that some of my songs on the USB drive were in other file formats like mp3 and were unplayable by the honda head unit so I used a program called "switch" that can be configured to overwrite the mp3 files and saved in the folder hierarchy as a converted aac file.

Both programs are free and for the mac.

link to itunes export

link to Switch Sound Converter