I haven't worked in a maternity hospital for about a year, but this is what used to happen if I got called to assist at a suspected meconium aspiration.

Once bub was born, no stimulation ie no rubbing down, bub placed on resuscitate cot and a pediatrician would look at the bub's vocal cords with a laryngoscope to check if there is meconium past the cords. If there is or they suspect there is, they will intubate and use that tube to try to suction out as much meconium as they can. They will also suction the mouth and nose. If this happens or how quickly it happens, or if they need to do other resuscitation methods depends entirely on the condition of bub.