First off it's not true that scent doesn't get into rubber, rubber can hold scent VERY strongly, however it's just not as prone to picking up scents and it doesn't put them off as strongly....(some rubbers, not used in boots, can have VERY VERY strong scent absorbing properties)

I usually silicone spray any of my codura stuff to make it a little more scent proof and more water proof, but I ALWAYS spray my boots with a scent killer before hunting, like after I get out of the truck and spray up, I leave a bar of scent eliminating soap in them usually too during lay times....I also spray the bottoms with doe or coon urine (scent) to help hide my odor before walking in. It seems to work, last season I was sitting in a ground blind with my legs kicked up on a tree just outside it, fell asleep and woke up to a 6pt grapefruit licking the sole of my boot!!! (code blue: doe in heat)