I currently feed mine 2x/wk. In the past I have fed up to 3 or 4 times per week. I recently rescued a GBTA from a horrible fish shop here in town. I've been feeding that anemone 4 or 5 times per week. You will find a range of answers, from a few times a week to no target feeding. I suspect that those who don't target feed have fish that they feed and their BTAs snag tidbits on a regular basis.
As far as types of food, I use squid, scallop, jumbo mysis, regular mysis, shrimp, silversides, lancefish, and krill.