British journalist Mehdi Hasan suggests using these three steps to beat the Gish gallop:
Because there are too many falsehoods to address, it is wise to choose one as an example. Choose the weakest, dumbest, most ludicrous argument that your opponent has presented and tear this argument to shreds (also known as the weak point rebuttal).
Do not budge from the issue. Don’t move on until you have decisively destroyed the nonsense and clearly made your point.
Call it out: name the strategy. “This is a strategy called the ‘Gish Gallop’. Do not be fooled by the flood of nonsense you have just heard.”