talking to a farmer gearhead today that told me how he has unsiezed engines that have locked up.
he built a adaptor that can screw into the spark plug hole and then hooks it up to his tractors hyd syst . he advised that he gently apples pressure to the motor with all other cylinders oiled down and no matter how bad the motor it will move.
i asked him what was left after that and he advised it does not seem to cause any severe damage unless the engine was complety crapped to start with
he just kepps going from cyl to cyl and slowly turns the motor over .