No. You don't activate a pokebody, it just happens. So, all of your grass pokemon, excluding any shaymin, get an extra 40 hp. You don't turn it off, then turn it back on next turn, it just happens.
RE: My list (I Want Flygon LV.X!!)
Your BTET Team Galactic's Invention 107 x 2 for my RH Buck's Training, RH Cynthia's Feelings and RH Cyrus's Conspiracy. LMK. I have more RH trainers if those aren't to your liking.
RE: CATBUS: [W] Weavile G [H]: JPN Merchandise, Dialga G X, Shaymin Land Lv X
Your Shaymin Land Form Lvl X for my Rampardos pt x3 and Weavile G. or CML. LMK. thanks.