SILK for NUKE is a new take on a old-school effect, created by doing a Convolution v Median filter. With a ton of pre and post processing, you get some quite interesting looking silky streaks. Because of the convolution based approach sticks to the footage as seen below.
The number of streaks is directly proportional to the area of the Median filter, and the size of the streak is proportional to the size of the convolution. The final look of the streaks will wary depending on the convolution algorithm. One of the most pleasing ones is the classic gaussian blur. You can also use others filters like erode that will push and pull the streaks away from each other. There is a detailed look at all the algorithms included in silk in the video below.