So, you want to hand-crank your engine? You want to know how to do it? WHY?
Hand cranking is a skill that our fathers needed to get the Tin Lizzie, farm water pump etc., going. It has been lost in the passage of time. Like running boards on cars and kick starters on reliable motorbikes, hand-cranking has had its day.
Hand cranking requires practice.

My first piece of unwanted advice is to avoid hand cranking at all costs! It is unhealthy! It can bring on a heart attack, break your thumb or bark your knuckles. None of these activities are welcome at any time, let alone 400 miles offshore.
There is no substitute for a well installed and well maintained engine.
So, you still want to do it? OK!

If you can't do each one of the following without fail, you are deluding yourself. If you can say yes to each question go ahead and crank your engine.

1. Are you physically fit with a strong cranking hand and arm, no back or leg trouble?
2. Is the engine supplied with a cranking mechanism from the manufacturer?
3. At any time you may need to crank the engine can you remove the engine cover, stand in front of the engine in a braced position in a heaving seaway and rotate the engine with an unmodified crank handle a full 360 degrees without touching any part of the boat with any part of your body?
4. Yes? Looks like you're ready!

NOTE: The fuel injection pump timing is no longer optimized for hand cranking the engine so it is a little more difficult than cranking an engine that is designed primarily to be hand cranked.

OK, brief your for'ad hand on how to open and close the decompression levers. Begin by asking them to open them all so you can easily rotate the engine. Tell them to drop one lever when you get up to cranking speed. Don't warn you when! When it fires twice they can drop the next lever... then the next lever. If your levers are connected by a bar, remove it for this exercise, it is for electric starting with a low battery.
Now it's your turn. Fuel is on and bled, sea cock is OFF. I hope you are not bare foot or wearing those 'Samoan Safety boots' - thongs, jandals or sandals? Do some body stretches. Stand in front of the engine and grasp the handle with your fingers around the handle and your thumb pointing along the handle, toward the engine. Start cranking as fast as you can, remember, your job is to pull the engine through the first compression, so as soon as you feel any restriction PULL HARD, don't stop until the engine is going faster than you can crank. The tendency is to slacken off, which is why I recommend the 'cranker' doesn't know when the levers are being dropped for the first few times you start the engine like this. Once you get the knack it is a lot easier.
Now that the engine is running and the emergency has been resolved, very lightly oil the handle, wrap it in an oily rag and seal it in a plastic bag. Stow in a safe place till you need it again, in about 20 years time...