I had a bad outbreak one time. I tried nearly everything (kalk paste, lemon juice, boiling water, nudibranchs (I had a wrasse and I think he might have ate them SOOO...)). What worked for me was going down to the gulf in Texas and collecting like 100 peppermint shrimp. For big aiptasia, I killed them with lemon juice. The peps at all the little ones. However, I was then left with a large population of peppermint shrimp that would munch some on LPS and softies (anything really).
I would say nudis are your best bet but they're expensive and if you have a wrasse, they may get eaten before they can do anything. I would just reboot my tank before I used solely aiptasia x, kalk paste, lemon juice, etc. If anything, I think those products just stress them and they release some slimy stuff (highly technical term) that make more aiptasia. It's anecdotal but it seems like the more I tried to spot kill them, the worse they'd get.