From time to time you might want to blur objects in a video such as people, license plates, home addresses etc. Here is a quick video on how to do this using effects.
Steps:
Add Mosaic effect to clip using the fx tool

Edit effect, change Horizontal and Vertical blocks to 50, the Draw a box, circle or pen selection over object and choose Track. Tip: make your clip small or the track tool will analyze the whole clip which may take a long time.
