Mine is a 1989 190E 2.6. I bought a cheap 3/4 inch drive breaker bar and 28 mm (I think) socket. I locked the crank with a big bar of 1/4 steel with a hole drilled though, and a bolt into one of the holes on the flange. A smear of grease on the socket allows for an accurate torque reading (the socket prevents the crank from rotating). The bar is against a piece of 2x4 so it does not damage the bodywork. The bolt came off like nothing. Putting it back on, I just hung 200 lb. (myself) from a point 18 inches along the breaker bar.
I don't recomend using a pipe wrench on the camshaft to turn the engine, like the previous owner did.