Not a veteran, but been trying to get a bunch of Thralls together myself.
10pts into Strength helps for “Thuggery” when using Truncheons. But I also have a high Strength build to begin with.
Also, getting Iron or Steel Truncheon is much better because the base one is pretty sh*t.
Another thing to help out on is the “Blunted Weapon Fitting” upgrades that can be crafted in the Blacksmith station. It comes in several different grades but they “increase concussive damage” quite well when used on a Truncheon. I got a “Simple” quality one made out of 10 iron bars fitted to my Steel Truncheon and it works wonders. Coupled with my high Strength, I can knock people out real good now.
Also, if you have a Thrall to spare to follow you, you can craft an additional Truncheon and have him equip it instead of his regular weapons, when you are getting to a spot where you want to knock out people. Whether it’s one NPC to gang up on, or having another to help you out tackling 2, either way, it’s another Truncheon swinger helping out.