However, like many 2 finger pickers he uses many of the same tunings clawhammer players use (i.e. he ventures out of open G a lot). His tab for Cold Frosty is in modal tuning (gDGCD with a capo on the 2nd fret - you can get there from open G by tuning your second string up a half step).
I didnt see a tab for Angeline on his site - you may be able to find a clawhammer tab and adapt it to 2 finger index lead by up-picking the normally down picked notes and just picking a single note when you see a brush listed (though I suppose you could do an up-picked brush too? Not sure if index lead pickers do this or not) I met Chip once at the Floyd Sunday jam and he said that he thinks of clawhammer as a "modified 2 finger index lead" style. Again, the clawhammer tabs you find are likely to be in double D (gCGCD capo 2) rather than open G.