I think it's one of Joey's "bend 2 strings very close together, and bash the hell out of them" techniques. Forum member Derek Olsen (ProverbialCereal) may have more insight on this. He works out the chords and tablatures for the Pixies/FB songs on this site. This may even already be tabbed out in the Tabs/Chords section.
i asked pretty much the same question not long ago in the TABS AND MUSICIAN forum. someone very kindly provided this tab, which seems pretty good. sorry that i can't remember your name. also, this tab is only from memory, so excuse any mistakes.
I could be wrong, but I believe Joey strikes on the strings behind the nut way up by the tuning knobs, over and over.. The best way to confirm what he does is see it live, which I have not done yet.