Nirvana

I dont know much about Nirvana but it sounds like a pick.

 

both actually, it depends on the song

 

On MTV's Unplugged he played with fingers.

 

in most of the videos he plays with picks

 

depends
in lithium for example:
fingered upto bass solo (i think)
then deff pick from then in

heart shaped box was deff fingered
come as you are deff pick

its hard to tell i've just seen pictures
so it isn't going to effect your playing alot

if you do finger and want his sound try playing with treble (amp) tone (guitar)
later

 

smells like teen spirit is definitely a pick