I haven't used a base coat yet, but I heard that using it will speed up making the clean edge so most of the brand use it for their products. If it is true and there is no disadvantage of it, I would rather use it instead of repeating a number of grinding and edge painting.
However, Peter does not use it in his edge paint tutorial, and I feel like using a base coat is a kind of compromising the quality. If you have any exprience or information about the base coat, please share it so that I could use it in appropriate situations. :)