The big thing to remember with these foams is to NOT put it on so thick that it takes forever to dry or make what seems to be not drying areas that end up with air pockets.

If you need to design in large areas like making a tree, do it in layers adding a new layer over one that has completely dried.

You might also find it pulls off the glass as some parts expand and others contract during drying.
If its a visual spot, you can either fill in with more GS or you can trim the GS back to add in silicone and substrate to hide the GS on the sides.

Look through some of the journals and see what others did since some silicone before the GS to hide the white color and others like me don't.