I think you could use most anything to hide a pill in. You would be using only a small amount right? So, you shouldn't be adding too much protein to his diet no matter what you use. I think a small bit of american cheese or some bread (if your dog likes these) would be fine. I would even use some chicken baby food also - my dogs love taking pills in baby food. Purina NF also comes in a canned food, and you could hide the pill in a ball of canned food as well.
This is just my opinion, so you may want to just give your vet a quick call to make sure they are fine with whatever you choose to hide pills in.