Pretty tough to get permission by asking landowners. There are probably 3,000 students nearby that hunt and think they can drive up to a farmers house and ask to hunt their land. I would try some of the feel free to hunt areas, but the remaining 2,990 student hunters (those that don't get to know the locals) hammer the feel free areas pretty hard.
I would suggest driving as far away from Pullman as time allows, 20 miles at least, and try there.