I have just started using coffee grounds and broken eggshells and I will be keeping an eye out to see if it works. Have previously tried beer but the sight of 30+ drowned slugs was a bit too boak inducing for me to continue! I have noticed they also drown in water after I left a bowl out for the birds!
Copper tape works 100%, but is quite expensive. Apparently vaseline keeps them at bay, like the idea of the 'cloche', perhaps with a smear of vaseline round the top? Vasleline is waterproof too. My snails get magically transported over the fence to the neighbours... disclaimer: they have a tree and shrub kind of garden