WICavy - I know the seeds seem to work for your
cavies, but I still would never recommend them to anyone. It only takes once for a seed to get stuck on a pig's tooth or in their throat, for it to cause choking and possibly death.
Amsley246 - While it's very true that you shouldn't feed coconut to your
cavies, using a bit of the pressed oil, gently massaged into dry spots on the skin, shouldn't be a problem. There is very little chance of them ingesting much if any of the coconut at all if any should be licked. The reason I mentioned the licking is that it is a vegetable product and non-toxic to the pigs.
gooberific - I'm not sure about the grapeseed oil. I know they can eat grapes, but not sure if there is anything in the seeds that they should not have. Maybe someone more knowledgeable will come along and answer that question.
NOTE: I combined the two threads about dry skin treatments, so people would not be responding redundantly. Both threads were started so close together, people may not have realized that the other one existed.