I agree this works as I have done it in the past.
Another slightly more mechanically sympathetic way is to use heat soak from the engine. First check to make sure your clutch is working OK; then just start engine in neutral and use something to hold the clutch pedal down all the way, a stick or breaker bar is ideal, wedge the free end against the front of the drivers seat. It can take up to an hour to free off as the engine warms up the clutch warms up, freeing off the clutch plate from the flywheel. You will suddenly hear a "thunk" noise and she will come free.
What I have done in the past is to set her up with the clutch down and then work on the engine timing (strobe), mixture, airfilter etc. so that I'm not sitting about getting bored.
If you are feeling brave, you can jack up one rear corner in 2WD on an axle stand and leave her in first as the gearbox and rear axle drag will help the process. When the rear wheel stops turning, she's come free.