If there are no pigs in his area thats going to spook the deer even more than the smell of rubber. dig a hole just big enough to put the boots in, and burry them for a week or so, then from that point on use fresh earth cover scent on them or maybe even some fox urine, I advise on staying away from any anti-ground scents such as coon.
ORIGINAL: RJPOUTDOORS
Find a pig farmer and get some pig sh t in bags. Place boots in it for three days then clean with baking soda. For the inside put baking soda in them this should go the trick.
Good Hunting.