So I've taken a little heat for my firm stand behind the 'spirit model' of magic in my previous post. As I said, my approach is a thought-experiment, a deliberate effort to think my way back into an animist mindset. As such I tend to speak affirmatively, even categorically. That's a rhetorical pose, and doesn't really reflect an opinion on my part that my ideas are 'more true' or 'better' than some other model.
Honestly I think myself mildly clever for devising a rationale that merges the modern notion of constructed entities with the notion of pre-existent spirits 'conjured' by a sorcerer. Like so many techniques the form of the work doesn't need to vary much per model. What we 'believe' about what is happening may be one of the least important parts of the business. Nevertheless I like to decorate the inside of my head with the ideas and mental postures of ancient magicians, and I'll take my best guess and apply it.
My intent in bringing up this topic was practical. I consider the 'servitor' technique one of the more valuable modern inventions, and it should/need not be abandoned by those attempting to work in the models of the ancient world. Jake Stratton-Kent is heard to say "Magic is practical eschatology". The merging of the spirits of the un-individuated Dead into that great continuum of shades, called "the Dead", roiling with the mixed passions of human memory becomes a kind of 'magical energy', able to respond to the will and word of magicians in much the same way as Levi's Astral Light might do, though perhaps with more volition. It might even be, as some spirit-sects maintain, that the magical work of granting individual form and name to elements of this daemonic continuum is a service that living magicians do for the spirits - a fair exchange for their aid in our works.
Nevertheless, my intent here is practical, to provide this little set of suggestions as to what forms and symbols might be proper for what sort of spirits. I have ventured some ideas about classifying spirits according to an older set of 'elements' and this list fits directly with those ideas. All questions of models aside there are so many creative and exciting ways to apply this sort of practical conjuring.