Sounds like you would have better luck just taking the live rock out and catching them all at one time than to use a fish trap.
I just bought a fish trap but it won't work for the bigger sized fish you have. All it is is, a mason jar with a energy drink top cut of to fit inside of the jar, sealed with a rubber band around the plastic bottle top. Maybe you can come up with something from around your home.
Well, the fish trap that I got caught my peppermint shrimp and some of my snails... no DAMsel though. I think he's just too smart to even get near the jar trap. I'm going to have to tear the whole tank apart to get him.