Tigerhunter: Kneel down at the rub, placing your eyes about same heiight as deer's head. Look directly upwind to the furthest point you can see at that level, yet still be able to see the rub. Go to that spot and pick a point crosswind that you can get a shot into that spot. Often, with BIG rubs, the rubs are placed in locations that the buck NEED the does to be, such as a wind transition area. They will view the rub from upwind location, and move in when they see does near the rub acting normally.

You might just intercept the buck at that upwind location.