A problem with using a desiccant is they absorb water quickly and must be dehydrated quickly or they add moisture to the air in the safe. I used them in conjunction with my Golden Rod when I got my first safe but I was always having to dry the desiccant. You really don't need it as long as you use a heat source inside the safe and make sure your guns are oiled. And I prefer my Golden Rod to a light bulb because it doesn't put out too much heat and it has never burned out (27 years and going).

Here in PA, I coat the steel parts inside & out, with Birchwwod Casy Sheath, then put them in a Gun Sock which is impregnated with silicone, then put them in a gun safe that has a Brownell's silica-gel canister in it. I de-humidify the silica-gel canister in the oven for three hours about once a month. Have had no rusting, either here or in upstate NY using this approach.

The small lightbulb trick is one we used in our wall-lockers in Vietnam, and it prevented rust and mildew both.

I didn't have to recharge mine too often, but I did put some foam sealing sttrips around the door edge.
JCN