How do you add another iPod to your iTunes but not have all the same songs in you library be added?

My brother wants me to add songs to his iPod, but I don't know how to do it without adding all the songs on the iTunes Library. I know you need to check/ uncheck them, but its a hassle... Is there anyway to create a separate library or something for all of his songs and another for all of mine?How do you add another iPod to your iTunes but not have all the same songs in you library be added?
once you connect your borther's ipod you have to click on his ipod and go to summary-options- and check manually manage music and videos