The towel is something I use when I take care of him after taking a bath and the tortoise does it once in a while, usually a good 30-60 minutes inbetween
I use a mixture of sand and coconut fiber which I wet and let sit for an hour then i mix it and put it in their cage, as to their UV Bulb I use a Mega-Ray Mercury Vapour Lamp which I got when I bought them from my pet shop.