Instructions
Capturing a Shiny Shellos
Travel to Route 213 and place a grass-type Pokemon at the front of your party.
Walk around the tall grass until you encounter a shiny Shellos.
Use Grass-type moves to weaken the Shellos and then capture it. Do not defeat it, because then you won't be able to capture the Shellos. This may take you some time; the chance of encountering a shiny Pokemon in the wild is 1 in 8,192.
Breeding a Shiny Shellos
Capture any blue Shellos and note whether it's male or female.
Use the global trading station to get a blue Shellos from another country that's the opposite gender of the Shellos you caught in Step 1.
Travel to the Daycare Center in Solaceon town and deposit both Shellos.
Walk around the town until the owner calls you back. He'll give you an egg.
Walk around the town some more until the egg hatches. If you're lucky, the Shellos will be shiny. Although it's rare to get a shiny Pokemon, the Masuda Method quadruples your chances of finding a shiny to 1 in 1,365.3.