He also reiterated the use of straights vs. curves. On the hand there is always a straight side and a curved side. The fingers are straight in the middle and curved on the outside. The palm is not flat but has a slight arc. The arc is only gotten rid of by external force - which pushes a fat pocket on the side. On the hand and fingers the bottom is fleshy and the top is boney. He quoted Glenn Vilppu stating there is a flow from the arm to the middle fingers - if you don't draw it the arm will seem broken.
When drawing the hand it's not that important to have a lot of information on the inside it's important to have good design on the outside. Kevin said to study animation drawing to understand the hand. Kevin also told us to be aware of making the fingers too sausagey. He said to think of the finger as a box.
I've never really heard anything that I can remember about the proportions of arm and hand. Today, Kevin divided the lower arm into thirds. And then the 1/3 measurement could be used as the measurement of the palm and that measurement again with the same distance from the palm to the top of the figures. He also talked about the thumb coming out a 45 degree angle.