SMOOTH:
The handshape starts as a "flattened O." Move both hands forward. The thumbs start near the pinkie and slide over the fingers. The handshape becomes an "A-hand" as the hands move forward.
SLICK / smooth:
The thumbprints start touching the prints of the middle fingers. As you move the hand forward the middle finger bends more and side of the tip of the middle finger slides down along the thumb.
Notes: