Now do I just use AlignToVector to make an entity "snap" to another entity's vector?
Eh? Entities don't have "vectors:" they have a rotation (pitch, yaw, and roll) and a position (technically, position is a vector, but I'm fairly certain that you don't mean to use one entity's direction-from-the-origin for aligning a second entity.)
I dont understand what you're trying to do. Please elaborate.
If you want to reset an entity's rotation to be the same as another entity's, you could RotateEntity(d, EntityPitch(s), EntityYaw(s), EntityRoll(s)), but I suspect there's a better solution to your specific problem - probably to do with parenting.