For candycanes and other large polyp corals, you can feed mysis shrimp or some other large size food. They will eat it up. You don't really need to feed them, but if you do, they grow way way faster (in my experience.)
Use a plastic pipette and spot feed them, just shooting it at their tentacles (so for candycanes, you might have to do it after lights off once they open)
Xenia: don't feed. they grow like weeds. You can shoot something at it if you want to, not sure what size they like though.
Zoanthids: some of these eat, some don't. You can shoot stuff at them if you want, not sure on particle size.
small polyp corals: I've used to use oyster feast (oyster eggs and ovarian tissue). Follow the directions, and you can spot feed.
With that said, what I've been using now is Rod's Food (standard formula.)
It has all things above in it plus lots more stuff for variety. I just feed that. Spot feeding when I feel like it. It has small stuff down to SPS level all the way up to small chunks of meat (shrimp, squid, etc.)
I thaw it in a shot glass. The heavy stuff sinks, smaller stuff stays in suspension. So I can take the fraction I want for feeding, or I can just mix it all up and feed the tank. The food will blow around (as I don't have any mechanical filtration besides live rock), and the corals are great filter feeders, so they should get their share.