My duck's eggs are waxy, not sticky. When the ground is damp (very often here in swampy South Fla) they get dirty where they're laid on the floors of the duck houses. But when it's dry they often stay fairly clean. I collect them as dirty as they are, try to wipe off some of the larger clumps of muck off while it's still damp. I don't wash them until right before I use them or sell them. I run warm water over them & use a plastic scrubby to get them clean.
I do the same thing for chicken eggs IF they're dirty. Often they are clean in the nest, and need no further help. I never sterilize them with bleach.
I agree, the trick is to find the right market, folks who know the benefits of duck eggs. Sometimes I'll add a few free ones with a carton of chicken eggs, just to let them try them. Some folks just don't like them or appreciate the difference they make.
Many chefs or bakers won't pay extra for duck eggs, even if they themselves appreciate the difference, because they cannot charge extra for the goods baked with them.
I myself would like to make money by setting up a Duck Therapy Spa. I would set up lawn chairs in the shade and give people a bag of thawed frozen peas to attract the ducks. Then they could relax in the shade and enjoy watching the ducks going about their birdy business, quacking & flapping & waggling tails, while their stress melts away and their blood pressure drops to a healthy level. How much would YOU pay for a service like that?