Standing on featureless rock through friction alone, with no actual hold — placing as much sole as possible.
In smearing, rubber replaces the foothold. The angle decides it: drop your heel so the ball of the foot lies flat against the rock and as much sole as possible makes contact — the flatter the angle between sole and rock, the more friction. The instinct to go up on your toes and hug the wall is exactly wrong: it shrinks the contact patch and pushes your foot off. Second point: commit your weight to the foot and stay there; a half-hearted smear always slips. On friction slabs this quickly separates those who trust their legs from those hanging on their arms.