Instead, they made sure to shoot just enough angles to get Rocket into a scene, and then they pretty much just cheated the rest.
Vol. 2 wasn’t a production like Alien: Covenant — which used high-tech cameras to keep Michael Fassbender in two places at once.
From there, Gunn simply kept himself ready to actually portray both characters and deliver full-fledged performances for each of them whenever necessary, even though Bradley Cooper’s voice eventually wound up in the final version of Rocket.
Like so many other parts of life, it sounds like the trick to playing Kraglin and Rocket in the same scenes involves finding the easiest possible way to get a shot.