I have had some issues with craftfoam and gesso-like materials of different kinds. Mostly because gesso is not very flexible, so it doesn't go well with craft foam. It just snaps or breaks.. No good "putty" material is flexible, right? If it is like rubber you will not be able to sand it down which is the whole point of it, sanding it nice and smooth. But what about plastic? Plastics are somewhat flexible but still hard and possible to sand. I asked around a lot looking for plasti-sands and bondo of different kinds. At last I found a possible solution: Plastic Padding.
It seems like this is a good alternative and it is:
1: Sandable.
2: A bit flexible. Not as flexible as the craftfoam but it is more like plastic. A thiiiin layer of this might break but if you reinforce the craftfoam first so it doesn't bend so much it seems to be fine.
I have applied some Plastic Padding to the rough edges where the craft foam and the wonderflex created uneven edges. Once I sand it down it I hope it will be really nice and smooth!
