I just read about someone on the same meds and they use Boudreaux's Butt Paste.
It is a very common side effect for incivek, to me the incivek seems to leave an oily residue that the TP won't take off, so as soon as I'm finished with my business I have been cleaning the area throughly with soap and water then pat dry, then use a tucks pad maybe 2-3 times thoughout the day and it keeps it well under control. If any oily residue is left behind it continue's to burn and for me is quickly noticable.