Happened to stumble across this after playing Spooks. Not sure it's worth replaying to a six year old thread, but what the heck.
The only way other players can stop this is by holding back blues also but you will find most are not willing to do that.
You don't have to play blue to follow a blue - you can just as easily play a red or green card of the appropriate number.
Goblins: It is pretty simple but if you have really low goblins hold onto them. That master bat may come out later making those goblins very valuable especially if you play with the goblin dump variant.
Wow! We never realized that the Master bat flips the goblin trick values as well! Cool to know.