No Heat Service Call Plugged Steam Return

My customers notice no water comes out of the heater drain valve. Also not sure the steam boiler sight glass is full. First I notice the water sight glass overfilled. Therefore I remove the valve that isolates the sight glass. Water drains out the valve with force. I verified the steam boiler water won't come through the drain. I hit the side of the drain and return pipe a few times. Unfortunately, the plugged return doesn't break up and water drains. Now I remove the drain fitting and withness the return pipe full of mud. I grab a zip tie and snake through the clogged steam boiler return pipe. Water starts draining breaking up and flushing any remaining gunk.