It's great to play those Smith/Mangum songs alone, in your room. But it's taboo to incorporate them into your set. Mostly, it's because it's never been done successfully, but I'm sure that most people find it somewhat cringe inducing to hear their songs played by other people.
And as for Okkervil River, I am definitely recommending 'For the Captain'. I basically lose my voice every time I decide to play that one to myself. I guess 'No Key/No Plan' would be the easiest of their loud songs to play/sing/learn/enjoy if you're not familiar with them. Whenever I try to play 'Black', I get far too into it, lose all timing and stop trying to sing and just scream out the whole song. Is that perhaps why it is the song he SHOULD be playing?
I did a youtube search, JUST for you!
http://youtube.com/profile?user=Cougarman7And it brought me to this guy. He plays songs on his acoustic guitar and teaches you how to play them. Popular and accessible stuff! I found myself watching his videos and I very much enjoyed those Wolf Parade songs particularly. I think that if you learn those, but growl them instead of singing, because I didn't really care for his singing, you could have a hit on your hands!
Addition: Do you have a capo? They're pretty important. You should learn how to tune down too. They're both useful things to be able to use, especially if you can't really sing.
Hey guys, how do you pronounce that anyway? I've heard it pronounced either 'cap-oh' and 'kay-po' from all kinds of people.
Edit: That guy is now teaching me how to play Will Oldham songs!