Yes, piepatch, I do use a walking foot.
I use Insul-Brite as the bottom layer. I do need a total 2 layers of batting because the Insul-Brite is not enough to hold on to pans very long.
My second layer is a polyester felt. It's thicker than flannel or interfacing.
It's layered as: Cotton design fabric, Felt, Insul-Brite, then backing cotton fabric on the bottom