There are no special rules for ancestor spirits as far as I know. Presumably you'd handle them with normal thaumaturgy effects. 7 shifts of Lore skill substitution gets some ancestor ghost to give you Epic-quality information about Lore, and so on.
And IIRC Ghost Speaker lets you contact ghosts the same way you contact living humans, so that's an option.
If you want to summon them and have them fight for you, you might find this and this useful.
I'd handle this the same way, minus the summoning rules.
If you have an ancestor spirit like Sir Stuart, make it an Aspect you can invoke. AS far as multiple ones, I'd say it's possible but unlikely, given the nature of how ghosts are created and stick around in Dresden...of course, a sort of "Spirit Council of Elders" is a really cool concept. If you have refresh to burn you could make them an Item of Power.
Instead of Summoning Rules, I note that Mort gets tired when he directs ghosts on-the-fly and the prevalence of thaumaturgic-level magic with the speed/method of Evocation. This tells me that you can pretty easily model what he does as Ritual: Ectomancy, and Superior Ectomancy, effectively using "Ectomancy" as an evocation element in combat. Availability of ghosts to do this is handled simply with compels.
Spinning off the idea of a "Spirit Council of Elders," here's how I might build a "21st Century Shaman" ectomancer at Chest-Deep:
HC: 21st Century Shaman
Trouble: Still An Outcast In Society
OA:
- I HAVE to Listen to My Elders
- The Old Ways Aren't The Only Ways, But I Still Keep A Beard
- Last of the True Ainu Shamans
- I Named Him Smokey
Skills:
+5
+4 Conviction, Lore, Discipline
+3 Endurance, Survival, Athletics
+2 Stealth, Fists, Alertness
+1 Presence, Rapport, Scholarship
Powers:
-2 Ritual: Ectomancy
-2 Superior Ectomancy: You may perform Ectomantic rituals with the speeds and methods of evocation, and your focus items for rituals may be used in conjunction with this, substituting Complexity bonuses for Power.
-1 Item of Power: Ancestor Spirits
+1 One Time Discount: It can be found and scattered, but its purpose isn't obvious to everyone, and it isn't carried around.
-0 It Is What It Is: A shrine in his home housing seven carved sticks that act as vessels for his relatives, who offer guidance and wisdom.
-0 Unbreakable
-1 Guide My Hand (He may use the powers in Guide My Hand after praying and speaking with his ancestors for guidance at the shrine.)
-1 Occultist: Spirit Beings (Kamuy)
-1 Item of Power: Smokey the Bear Spirit
+0 One Time Discount
-0 It Is What It Is: A bear spirit invisible to all but those who can see ghosts.
-0 Unbreakable
-0 Wizard's Constitution
-1 Echoes of the Beast: Bears
Focus Items:
Elm Staff: +1 Ectomancy Control
Enchanted Items
- 2 potion slots
Starting Refresh: 8
Refresh Spent: -6
Remaining Refresh: 2
