I grab a shot glass, fill it with tank water and drop in a chunk of frozen mysis and then fish out the mysis with a pair of chopsticks dedicated to the tank. I sink the chopsticks in to get some mysis into the current where the chromis feed, then I drop them a bit lower to make sure some get to where the clowns feed near their cave.
I always let it thaw out first... I fed a cube of frozen brine to my fw tank a while back and watched my gourami spit out pieces of brine as they fell off. Too cold for his taste.