After you grab the Goron's Bracelet pull out the stick that you already have and light it with the flame next to Darunia then side hop to the bomb flower connecting to the shop, once this is done superslide out of Goron City. Is this a faster method?
Bomb flowers take a long time to explode and HESSes are hard. It may not be faster and if it is, it may not be worth it. But who knows.
Don't forget that in any% you don't have a shield, so you have to settle for a FESS, which is slightly slower.
Yeah, i found that in the world record (by benstephens56) he could leave Goron city in approximately 28 seconds. While my test said that my best time was around 27 seconds... But that was after about 50 tries... So all in all if you can pull off a perfect FESS then you could escape in about (my time wasn't perfect) 2 - 5 seconds early, it's not worth it -.-
