As the post below says you do not need to vacuum seal the Mylar bags, as I stated in the OP you should vac seal once using normal methods then clean it to remove all traces of residue before putting into the non permeable layer. And yes I do believe hair straighteners can be used to seal, have a look at PlutoPete's listing in the OP for details of their system too. Really pleased to see this getting some traction and interest, it is long overdue!