score:4
Follow the "Correspondances" signs, and for terminal 2E whenever it's shown.
Clear immigration.
Keep following the signs for terminal 2E
Take the sterile bus to terminal 2E. The M gates are two stops away
Of course, if you know the incoming flight will be delayed, speak to the cabin crew, show your connecting boarding pass and they may be able to arrange transport. Once at CDG (where I entered Schengen) they even stopped at a special border control booth located outside, where the police glanced at my ID card for a second before letting us on.