You don't really need to do anything to them. They're survivors! They're biennials or short lived perennials. They grow from seed and flower in their second year. Most plants will die after flowering but some may flower again in their third year as well. If you want to keep on having foxgloves in your garden you need to let at least some of them set seed. I just sprinkle it around where I want the plants if I want them to colonise a new area, or weed out excess seedlings coming up close to where the mature plants flowered. They do produce lots and lots of seedlings.

If you have a mixture of colours (not all the standard "wild" pink variety) it would be a good idea to dead head the "boring" or "standard" coloured flowers and allow only the "interesting" coloured flowers to set seed.