Most polyps don't need to be feed (zoe's, xenia, star, clove, daisy) since they either absorb their nutrients straight from the water or via photosynthetic reaction. SPS corals can be feed very small food (zooplankton, phytoplankton, rotifers, copepods, etc). LPS corals can be feed larger meaty foods depending on the size of the coral. Feeding in general will make the corals more healthy, but alot of the sps and lps corals also get a large portion of their nutrition via photosynthesis.
I normally use a turkey baster to squirt the food directionally where I want it. It also allows you to control how much each corals gets (too much can kill them, so the less is more method is best).