From what i recall they put a hose with a tiny hole in it to make the dpf look not as clogged to the sensor.
Then they set Rheingold ista or carly to do a dpf regen and then went for a long drive to clean it.
As said be careful of the temperatures, watch it with torque, ista, or Carly.... I'd think keep it below 650 C.

It's a shame these bmw complain about everything but don't bother to monitor a thermostat which really is bad!