Gosh, I don't rinse my eggshells.* I just throw them in a container I keep in the kitchen.* When it fills up I dump it in the compost pile.* If the compost heats up it should kill any bad bacteria.* I don't see why you couldn't get the eggshells from the local eatery.
I've heard of lots of folks who use eggshells for the slugs.* I've never tried it as I used beer.* I didn't like the look of the white shells in the garden.* If you use brown eggs that might look nice.* :)* I haven't had a slug problem since the toads moved in.
When weeding, the best way to make sure you are removing a weed and not a valuable plant is to pull on it. If it comes out of the ground easily, it is a valuable plant.