how do i add a playlist from itunes to my ipod without having to sync any of my music.

i noticed that you can select certain playlists to sync with but i just want to add them and not erase my other music. itunes wont let me drag the playlist onto my ipod but thats really all i want to do. i am working with a pretty slow computer that crashes alot so having to put all my music back onto my ipod (50ish gbs) usually takes awhile with many attempts. please help! again i stress i do not ant to use the sync selected playlists feature. as for background i have the newest itunes and a 4th gen 64gb touch.