There are different types of Bondo. You can get the pink bodyfiller, the green
"glass" version, and another resin jelly type. For dash fabs its best to use the green glass version of Bondo with the pink used on top for final layering.
anything large you could use resin or jelly with glass matte or cloth...
In your case Faiz Id use the green Bondo Glass version. (comes in a blue and white can) Thats if your in the US. BTW faiz - that could have been my post that you saw where I used the Bondo on my dash - and it was the fiberglass Bondo.