Ambipom uses Nasty Plot. Scarf Pelipper (with 1 point of speed less than Ambipom) uses Sky Drop on Ambipom. At the end of the turn, Cofagrigus uses Trick Room. At the end of the next turn, Pelipper finishes the attack, and then Ambipom uses Nasty Plot AGAIN. Cofagrigus goes last with another Trick Room at -7 priority. 3rd turn - Ambipom safely Baton Passes the +4 SpA boost to a defensive special sweeper (Milotic, Lapras, Vaporeon, Slowbro, Slowking, etc.), after which Pelipper protects it by using Sky Drop on it. The next turn, Pelipper comes down and the Special Sweeper wreaks havoc on the opposing team with Surf or Blizzard. Is that what you had in mind?
Note: This can also be done with the Regigigas (described above,) using Floatzel instead of Ambipom and Bulk Up instead of Nasty Plot.