On the matter of Ursacks & related bags: Over the past several years I've used the robust plastic Loksak and Opsak bags for food storage. They're advertised as odour-proof and, with a double seal at the opening, waterproof as well.
They've been durable, and while using them, I've never had any problem with critters attacking my panniers. That said, I still don't keep any food bags in my tent overnight.
BTW, on DEET as a fire-starter: The stuff I use comes in a small (37 ml) squirt bottle. So, no propellant. Brand name is "Ben's", made in NH. Sez it repels black flies, but beyond that falsehood/fantasy, I've found it works quite well.