Watch the Right Forearm Exercises online guitar lesson by Bruce Arnold from Guitar Physiology Survival Guide
There are a few more ways you can work on using your forearm as the initiator of pick motion. One is what I call the EKG method. You flip your guitar over so you have the strings facing you and you are going to play on the back of the guitar. You take a sheet of paper and place it across the back of the guitar. Replace your pick with a pencil and do your forearm movement while you pull the sheet of paper horizontally. This will show you exactly how consistent your picking is. Please note: Don't push too hard with the pencil or you could mess up the wood or the finish on the back of your guitar. You could also do this with a book rather than a guitar and is something I often recommend for high school and college students. As you sit in a class use either a pick or pencil with a sheet of paper to work on moving from your forearm. And finally as you walk down the street you can have you pick in your hand and do the forearm movement against the side of your leg.