I don't/haven't owned one, but here are the notes I have on multiball from the times I've played it. Hope this helps.

Creature MB: Ride ramp until 2-ball is lit at North Pole and R orbit. (as you get closer, the Lock 1 & Lock 2 lights will progress toward both flashing).
(1) Lock ball in NP. Wait for big "6" to display on DMD.
(2) Shoot lower R scoop (Geneva), NP, Ramp, or upper scoop (Sarcophogas) to lock in hurry-up JP value and start up to 6-ball MB.
(3) Shoot both Ramp and L orbit for JP's (but they can move if Move Jackpot shot is hit). Ball is added.
(4) Spell FRANKENSTEIN for 20M.
(5) Shoot ramp for 100M Creature JP. (incr by 1M/spin @ spinner)
(6) Shoot Sarcophogas scoop for 50M.
(7) Shoot SJP that cycles b/w L orbit, NP, Ramp, and R orbit.

Geneva MB: Not very lucrative. Spell GENEVA via lit lower scoop shots. Relight scoop via R orbit shots, or on a timer from R inlane feed. During GMB, 4 JP shots are lit for 20M each. After collecting each, relite them at Geneva scoop.

When I bought one I wasn't getting multiball either. Turned out that a switch on the ramp wasn't registering and that was stopping multiball from kicking in.