There are only two ways in/out of SWGE - the entrance by MuppetVision, and the exit/entrance that goes into Toy Story Land - there aren't any shortcuts per se that get you in front of the Chinese theater because of the way the backstage areas are set up. I'd be more concerned about how close you plan to cut it between leaving Oga's and seeing the fireworks - if they close off access to the back of the Chinese theater (by
Pixar Place) for safety you may have to walk all the way around no matter which way you come from. Perhaps someone who knows for sure can chime in on whether they close anything off during fireworks the way they do at Cinderella's castle in MK?