I've made lots of potholders and have always used one layer of insulbrite with one layer of 100% cotton. I imagine you could use 2 layers of 100% cotton batting...I just never tried it....I wouldn't want the recipient to get burned or hurt in any way. If I remember correctly, on one cup of coffee, I placed the 'shiny flecked side' to the hot side of the pot holders and the cotton batting to the hand side.
Check out the Warm Company:
http://www.warmcompany.com/ibpage.html
You could always make a sample of each setup and test it by lifting up a HOT HOT HOT pot!
Nan - Indiana