I shock with non-chlorine shock. It is an oxidizer. Just follow the dose size on the jar based on how much water your tub holds. Other people shock both chlorine and bromine tubs with just chlorine in the form of dichlor or liquid bleach by taking the level much higher than normal. That’s the 10-20 ppm you may be reading about. In both cases stay out of the water after you shock until the number drops back into the range you like.
