Add smoked ham hocks in a large 12 quart size or larger stock pot with 1 1/2 gallons of water,  boiling hocks  with lid on pot for at least an hour until the ham hocks fall apart.  Add more water if needed.  Remove each collard green leaf from the main stalk and wash each individual leaf until all dirt and grit is removed.  Strip each stem from the collard green leaf or at least the heavy portion of the stem and roll several collard greens together and cut into strips and place collards into the pot until pot is full.  As the collard greens wilt down, add more collards until all the collard greens are in the pot.  Add salt, sugar and chopped onion (optional to use), fat back grease (optional) and continue to boil for 1 to 2 hours until collard greens are tender.  Stir collards occasionally and add additional water if needed to keep the collards from sticking to the pot.

NOTES:  I read in Justin Wilson's cookbook, "Down Home Louisiana Cooking"  that some of his friends would use a washing machine to get rid of the dirt and grit from bunches of collard greens and my bride "Tweet" tried washing collard greens as above, but our washing machine was too powerful and the greens looked like that had been in a food processor.  It was a job to get the washing machine cleaned.  Go ahead and grin if you must!  Working smarter not harder did not work in this case.

Pix of collard greens on main recipe page, front right dish on the work station/bar island.