I have done this for my cleaner shrimp. My method was to pour the contents of the bag into a small bucket with an airstone. Grab a typical air line size hose and setup a syphon from the main tank. Purchase a screw type restrictor and attach to the syphon line and adjust it to drip a second rate. Give it 20-30 mins and that should be it. You can fish them out and pop them in the tank after that.
That's just my method tho....