I couldn't get my red and green one to feed at all when I first started feeding my coral. My neon green one still rarely feeds.
Some people may not recommend this and say it could harm the polyp, but this is how I got mine to start feeding with no negative consequences. Pick up a single mysis shrimp with a pair of tweezers and gently drop it on the polyp directly next to the mouth, but not on the mouth. He may slightly close up or not eat the first few times, but it should work eventually. If he doesn't start eating within a few minutes blow the food off gently with a turkey baster or something like that so it doesn't start to decay.
Also, it's always a good idea to feed the fish first. That way they won't steal food from the corals.