Your best bet of course, Phil, is to just buy a new printhead and quit screwing around with the old one.
If you must proceed with this torture, take the printhead out, covered it with a used white T-shirt, and run a vacuum – like a shop-vac in short pulses until you begin to see Ink coming out.
If that doesn't work, try putting the printhead under the front tire of your car. Back over the printhead slowly, then drive forward, then rinse and repeat several times.
If the printhead still will not work, go back outside with it, and as hard as you can, hurtle it against a nearby concrete wall. If all else fails, try scotch taping the pieces back together. Sometimes patience and perseverance and good technique, and these printheads can be salvaged.
Buy a printhead.