Call WDFW LE before doing it. Tell them where and when you want to practice. They really hate responding to calls unnecessarily. Then you would be as legal as the various fly casting lessons and Spey Claves that are and have been held on several rivers. As to hookless flies, that is what the casters at Occupy Skagit used during the demonstrations. I had my collection of hookless flies inspected by a LE agent before "fishing." It was a fun day a couple years ago when I had about a half dozen hits from bull trout that were chasing down pink salmon fry at Rockport. A couple of the fish held on to the fly for a couple seconds before letting the fraud be pulled away.