Kurt is like the Punchout of music. He didn't use a whole lot of technique, but he did very much with what he used.

Kurt was actually a pretty competent guitar player, technically speaking. It's just that the songs he wrote had no place for flashy solos and such. Granted, he was no Van Halen speedwise, but I've heard some rare tapes of Kurt playing bluesy-type stuff, and it sounded very well. But yeah, some people make him out to be about as good as someone who just learned power chrods.

That reminds me of Kim Thayil of Soundgarden. He played fast solos, but he didn't use any scales, per se. He once said it was funny to hear people call him a great guitarist.
It's pretty easy to get a Kim Thayil-like sound with a Wah pedal and some fast but fairly aimless picking. You can see (err...hear) some of Soundgarden's influence on Nirvana's Incesticide, namely the solo to Aero Zeppelin.