Welcome! I use permethrin, and when and if it becomes ineffective (not yet here!) I may switch to spinosad, which is also approved for use on laying hens with no egg withdrawal.
Rules change and evolve as more information comes available, so who knows what will be useful in the future?
Ivermectin works very well, and is easy to apply, which is wonderful. BUT it's not approved for laying hens here, because it will be in their egg yolks at some level for a long time. There are two problems here; developing parasite resistance to this drug, encouraged by underdosing, and those individuals extremely allergic to it, again, at very low doses.
Sometimes we do what we must, but think ahead, and don't use it just over convenience!
Mary