I feed mysis shrimp to all my LPS and I too feel your pain. I generally feed my coral with a long pair of tweezers (after I broadcast feed my fish).
My acans and euphyllia can fend off any onlookers but I need to watch my blasto, chalice, scoly, and lobo a bit more closely. I usually will keep my tweezers in the tank and nudge away my cleaner shrimp and small hermits always seem to encroach on my helpless blastos [emoji23] the whole process usually takes >5 mins and, IMO, its actually pretty fun... if the shrimp gets really feisty I usually hand him a fat price of krill and that shuts him up long enough for my corals to eat.
My hermits tend to be the real threat, as I'm always getting distracted by something else in my tank and all of a sudden there's shells stealing mysis from all the coral sitting on my sand bed[emoji23]