On our local radio station they have little segments of trivia, quizzes and such. And one such quiz the other day was "why put charcoal in a toolbox?".
And to get to the point people puts charcoal in because it absorbs the condensation and moisture and keeps tools from rusting. That was the first time I heard that but I'm going to try it, but I would put the charcoal in some kind of fine mesh that would allow the moisture in but help keep the dust from going through the tools when the charcoal got crushed up from banging around. Maybe charcoal briquettes would work too?

I'd be more inclined to use a desiccant... They make 'em in that come in a little tin with a window on it that tells you how "wet" it is, and you can recharge it by putting it in the oven for a few hours. I have several of these that I use to keep electron microscopy samples dry.