[Saber Cherry]

I always use scouts for bloodhunting. They are cheaper than anything except cheap blood mages with Sanguine Dousing Rods. If you intend to bootstrap into bloodhunting, you can collect 50 slaves with scouts, empower a national mage with synergistic paths (like Earth, Nature, Death, or Astral), forge a SDR, and hunt with him too until he's empowered enough to do useful things. Blood hunting with non-blood-mages was reduced in efficiency in patch 2.1x, but is still quite useful, considering scouts are dirt cheap. Hunting unsuccessfully does not cause much unrest, anyway, so don't be afraid to dedicate several 3000-6000 pop provinces to blood hunting, with 4-10 scouts each. You'll need to patrol at the upper end of the range... in the base game, I often use 25 indy archers and an indy commander for patrols (or low-end Foul Spawn); in a mod that sets militia pricing to very low levels, I use militia. But bear in mind that patrolling kills population much faster than blood hunting, so only do it in a very close game, a (anticipated) short game, early in the game to accelerate the bootstrapping process, with a theme that will kill people anyway, or when you choose some combination Disorder, Sloth, Death, and Hot/Cold scales that generate little income from the populace anyway.

Incidentally, scouts are still ideal blood hunters in many cases - even since non-blood-mage efficacy was reduced - because they are stealthy. Therefore, a scout transporting valuable slaves cannot be caught (when sneaking through unpatrolled territory), and a province full of hunting scouts can be set to "hide" when a pincer attack is expected... and lastly, if blood-hunting is your sole aim, empowered scouts retain their stealth and low upkeep while suddenly becoming able to use an SDR. Since blood-hunting is most economical in provinces you expect to lose (or at least, be unable to defend) rather than in your rearmost assured-income provinces, stealth and cheapness (in the event of death due to an unexpected attack) are immensely valuable to blood-hunters.