Killey's Johnny doc and Dustloop wiki Johnny page are both great resources for new Johnny players like myself and will get you started. Thanks to Killey, Brett and anyone else who has contributed to these pages!
Also, I guess most of you guys already know this, but you can execute mist cancels by pressing your MF button and HS at the same time when at level 3 for really fast and easy cancels. It seems to work sometimes on level 2 too, but doesn't feel as reliable as doing it normally.