I've dug some on Cambois beach before, but they are very quick, and you need to grab them almost instantly before they bury themselves back in the sand. Be very careful though if you dig them in summer months as weever fish also tend to bury themselves in shallow sand. I have nearly grabbed a couple when Iv'e been digging for sand eels.
Keeping them alive is a problem : try and get them in fresh sea water with an air pump as quickly as possible. ( a portable battery one is ideal when you dig them )
Also don't dig too deep, they are usually only a few inches bellow the surface. Never used a rake myself, but it would seem like a good idea.
And YES : they are a deadly bait for bass. The only problem once you have your eels; is finding the bass.
Good luck mate.