"From a zero figure to a sitting pose, without applying some other pose." Why not apply some other pose? Unless you're planning to sell the resulting pose, it's often easiest to apply a pose which is close to what you want, then adjust the bits that aren't right. If you want a hand or foot to be touching something in the scene, turn on IK for that limb, which will give you X, Y and Z translate dials for the hand or foot in question. Use those to position it, then turn IK off again. Sometimes conforming clothes do suddenly leap off the figure, even when properly conformed; try tweaking the pose a tiny bit, or move the figure very slightly, which often cures it.