Here's how I trained my Manderin:
First, make sure you buy come of those copapod in a bottle things and dump it in before you get him.
Next buy your Manderin!
After he's in the tank, let him settle down for a day or two.
Buy some kind of heavy duity airline tubing, along with a small syringe. The heavy duity airline tubeing I got from my LFS
for free. It's like a thick plastic that can be heated and bent. I will post a pic of my syringe setup when I get home.
Next, get your frozen brine/mysis ready. Suck some up in the tube using the syringe, and put it right in front of the Manderin. It may take some time, but he will eventually try it, and realize it is very tasty!
After a while, once you dip the hose into the tank, he will actually swim toward you expecting and awaiting you to feed him. You now have a trained Manderin.