I'm sure the chemical flush from MB is the best.
My '87 300E has never had a chemical flush.
I do change the coolant every year.
When new, I installed a Prestone reverse flushing "T" fitting in the heater hose.
After draining the coolant into a catch basin, you attach a garden hose to the "T" fitting.
You turn on the tap water ever so slightly and that reverse flushes the cooling system.
The flush water exits the top radiator or expansion tank filler, where the pressure cap is.
There are those who swear by MB coolant, I've always used Zerex.
I'm still on the original radiator and in 177,900 miles the second water pump.
The key is, coolant is cheap, parts ain't.
Happy Trails Beep Beep from change it in the spring Houston.
Donald, El Cheapo