Induct characters to support the cause => money, convince vassals
Evoke sympathy => make a character tolerant
Prepare grounds in a realm province => equivalent of current province modifiers
Trigger a Scoia'tael revolt against liege => the force of the revolt depends on the support/preparation, convinced/tolerant vassals would join the rebellion
Special force commander could discover members, similar to court chaplain job on heretics.
https://witcher.fandom.com/wiki/Scoia'tael The mechanics could be inspired by secret cults (https://ck2.paradoxwikis.com/Societies#Secret_Cult)
Special force commander could discover members, similar to court chaplain job on heretics.