I'm a big fan of the barbless hook method. There have been times there was NO WAY I was going to break down my entire reef to get a fish out. Just get some fly fishing line and the smallest barbless hook you can find. I got mine at a Sportsman's Warehouse, basically like a Walmart for sporting goods.
Anyway, what I do is dip the small hook into a piece of whatever your favorite food type mix is and then put it into the freezer for like 30 seconds. The small dab of food will instantly harden and it can be relied on to stay on the hook for 10-15 seconds before melting off once in the aquarium water. Or if your damsels are used to eating mysis shrimp or small pieces of meat, just spear that onto the hook.
The challenge is not catching fish in the tank that you dont want to

Give it time, you'll be able to do it. I've found it helps to feed the tank a little bit so all the fish think they are getting food, but dont feed so much they arent hungry. Then you basically watch the offending fish and when you're exactly overhead of it, quickly drop the line into the water. You'll almost immediately have a fish on.
Before I get hammered for inhumane treatment... this is the PREFERRED method for catching fish in the wild and most likely any fish that wasnt netted or cyanided (talk about inhumane) was hooked. I'm sure it isnt great fun for the fish, but a small hook shouldnt cause any problems.