There is a good tutorial on proper stropping in this honing and stropping excerpt from a barber manual in the SRP Wiki help files here. The stropping section comes after the honing. Among other things they recommend holding the razor on the strop and practicing flipping it without moving your arm. Just practice the flip between thumb and forefinger without bending the wrist. Some guys practice with a butter knife so they are less likely to cut the strop while they are learning.