the gaps and cracks will work well. i actually prefer the new foam by ge. i find that it cures with smaller air bubbes, but c&g will suffice. as far as control, there is very little. it will expand as it wants to. and the c&g will expand more than the others. get yourself a few cheap, dollar store steak knives for carving, they work well. although i prefer a combo of steak knives and various exacto knives and wood rasps.