Clawhammer, frailing, drop thumb frailing use down picking with the nail of either the index of middle fing and are best for the old timey sound. I prefer the nails to pick but I tend to have trouble with fingernails so I use either index or middle finger depending on which nail is in better shape. If they are both bad I use the Fred Kelly Freedom Pick. These can be customized with a file or sandpaper if you want a softer touch on the nail part of the pick. If you use the pick for up picking its best not to sand it to thin.

Cap't Bob