One other tactic to use, if you can kill one of your own models neer hamelin or a ret catcher, it will spawn a rat when it dies (which hamelin controls) you can then kill that rat to get points, and yes you need to do it before hamelin gets a chance to sac it, so use a companion chane etc, as long as you can keep the rat within 6" of hamelin/rat catcher, you can always kill the rat again when it respawns.
Collodi is great for this kind of thing, activate him, activate all the dolls, move them close to a rat catcher, kill one of the dolls then the dolls kil the crap out of the summoned rat, repeat, then move collodi back if possible