After the Duke sics his guards on you, fall down the Everfall (have to do this or your pawns won't be any use) then go back to the castle and get the guards to come after you. Now, hop up on a wall and just sit there. The Guards won't attack your pawns and they can't attack you. Your pawns will just keep murdering an infinite amount of guards. It helps if your pawns are mages/sorcerers because the defense of the guards is fairly high. Probably faster to go out and kill things yourself, but if you just want to idly rank up a job that you don't particularly want to play but need its core skills/augments then its nice to do this and go watch TV or something for a while.