I did the same. I bought 4 x 8 sheets of 1 1/2" (I think) thick insulation from HD. I then cut them to size and put them in each of the panels of my doors. I also filled the hollow channels with Great stuff minimally expanding foam. To put the panels in the doors, I had to cut them into two lengthwise pieces to fit them in. I used construction adhesive and then cauled the edges. I put the solver fol side facing inward toward the garage. It looks good and works well.
Tom