I have not found balsarite ( or a similar product by SIG) to be "soft". in fact ive used it to harden already in place soft balsa. good fuel proofer,also does great job on plywood or fiber glass center section. if your making a mess you are using way too much. small amount goes a long way.the newer product
( stripped can) is considerably easier to apply than the old stuff. there are coverings where you MUST use it as they have no adhesive . i wont cover with out it!!