A light feeding of manure tea, diluted fish emulsion, or a balanced fertilizer will help them grow lush and lovely. For container-grown succulents, I use one Moo Poo tea bag per three gallons of water, steeped overnight.
In-ground succulents don't really need fertilizer, but applying it does promote lusher growth. If this is what you want, spread Ironite before a winter rainstorm. And then in spring, apply a balanced granular fertilizer (like triple 15).
That's what many growers do. A little bit of fertilizer with every watering promotes rapid growth. However, such plants are considered "soft" (a nursery term) rather than "hard," meaning tough. It's a trade-off. I grow my succulents hard to help them better endure the open garden.
Soils vary from region to region and even within a garden. The best way to know what your soil lacks is to have it tested, but it's common sense that succulents growing in, say, oak leaf mulch are getting ample nutrients and don't need fertilizing; those living in pots for years or growing in decomposed granite probably do.
Amendments make a difference, too. None is as widely used by succulent growers and collectors as pumice (crushed lava rock). Here’s why.