This is a naturopathic method of cleansing or detoxification. I'm not sure it would help GERD unless you definitely had some problem with your gall bladder, in which case it may make you very uncomfortable and somewhat chained to the bathroom. Do you have a naturopathic practitioner guiding you? The idea of the gall bladder cleanse is really to relieve a "toxic liver" and I think other measures can achieve that, if you go with the idea that a liver can be toxic. A low fat diet without animal products or sugar or alcohol would "rest" the liver and gall bladder and this tends to be done with liver cleansing herbs such as milk thistle.
I did train and qualify in naturopathic nutrition but these cleansing methods are not so popular now and also the practitioner runs the risk of litigation. It's one of those things where the mainstream medical practitioners say either it's ineffective and has no effect, or they say it's dangerous and shouldn't be done at home . . . In theory if you had gall stones and did manage to flush them, there is the risk of getting a blocked bile duct, becoming jaundiced and having to trot off to hospital . . . . Have you had your gall bladder scanned?
Do let us know how it goes if you manage to complete it,
New stuff: GERD. Interstitial Cystitis
Lifelong stuff: Food allergies, eczema, asthma