The Pycolite for the shells works faster, I tried both ways. On the spot I said, it does wonders.
That is the most fun part of MC, collecting all the figurines:)
Buy one the Pycolite that makes you find more seashells, and go to the area on the route to castor wild that has a lot of grass, and do your job there. I suggest filling all three bottles with that Pycolite(I don't remember the color)