Nothing really universal due to the different types of head materials, i.e. cast iron, aluminum, etc.

"Hot tanking" is probably the best way for cast iron. Not worth the trouble doing it on your own. You end up with a bunch of nasty goo which needs to be cleaned up and disposed.

For aluminum heads, pressure cleaning is the way to go. The caustic chemicals used in most tank solutions can attack the aluminum. Machine shops not only have a higher pressure cleaner than the average D.I.Y.'er but THEY get to clean up the mess left behind.

You can usually strike a deal with the machine shop to have the head Magna-fluxed, straightness checked and vacuum tested at the same time.

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