Great suggestions. I also have Hans, which might be a really good pick against him too. Even if Brew is engaged in melee, Hans can shoot him and make him discard those precious cards he needs to get his debuffs up. I think that since I often take Seamus against gremlins anyway (unless he is absolutely not the best choice for the strat/schemes), he will be my most common pick against Brewmaster. I can also see McM being really good though too. If Brew goes first and stacks poison on something, then during your activation transfuse that poison off. If you go first, then brew won't have his defenses up and you can attack him. I like your idea of using night terrors, as they are good against other gremlin masters, especially Wong.