The easy way is using the Lesano potions from the Yellow Queen (Secret Garden Bookstore) to raise Corruption, which makes everything else easier. Ne mess, no fuss . . . OK, a little mess but you can deal with the Taint using an Embryl necklace. Otherwise, check the wiki, which says, in order to lower Willpower:
- Explain chores and sexual duties, preferably in a dominant manner (Talk > Explain something).
- Ask about sexual preferences in a dominant way (Talk > Ask something).
- By requesting sex in a dominant or sadistic way.
- Through degrading acts during sex and shower/bath events.
- Through bondage sessions.
- Through Frightening or Terrorizing actions (Talk section).
- Through the use of Butt Plugs
- An Educatorwith Corruption 60+, Dominant trait, or Malevolent trait 30+ can be given the option to Dominate their trainees, which has a daily chance of decreasing the Willpower of Trainees assigned to them by 1 (cap: 0) as long as the Educator's Willpower is higher than his/her trainee.
- Lecture (= preach) "Anti Willpower" in your Shrine, and all Followers will have a reasonable chance of having their Willpower decreased by 1 point.