I have never tried Tuco, but I am curious with what will be using his blasts to hit engaged models with black blood to give damage to enemy models.
For example, you have a nephilim beater engaged with an enemy, you shoot, and if you hit your enemy, you put a blast marker in your nephilim beater to spray black blood to the enemy. If you hit your friendly beater, you can also give the enemy the black blood and the blast marker.