I play bass too. grunge riffs are easy as. To play a grunge- riff dont think to much, just keep it slow and simple, using the E and A strings to create a heavy riff.
i would just try to play along some AIC and melvins stuff to get some ideas. or just try to play along with you favourite grunge bands for the ideas.t hat's how I try to get hold of a certain style of music. I just said AIC and the melvins beacuse they are my personal favorites in grunge. I guess some old hard rock like black sabbath, deep purple, blue cheer and led zep are great bands to get ideas from too, they were a big influence on grunge, you know?