Fast Skip is a reverse-flow control technique that is used to temporarily immobilise a target using shinsoo. It can be used at close to medium range, as shown by Jyu Viole Grace. With enough skill and power, one can freeze not only people but inanimate objects and even shinsoo. However this technique can be resisted and overcome if the target has very high shinsoo resistance or shinsoo control that exceeds that of the user.
This is apparently a rare technique, especially on the lower Floors of the Tower, and may be a difficult one to learn as Quant notes that it took him decades to learn it.