Would this solution work with my dehumidifier?
You got a strange problem for an outdoor storage building. A dehumidifier is gonna cost you a mint to run if the moisture problem is that bad.  Two things to think about.  First, where is all this moisture coming from? can you mitigate the source? Second, look at the gables or sofits to see it you can install some good venting. You can put a ridge vent on metal roofs and maybe a couple of gable end vents.  what kind of floor do you have?  A soil floor would be a good source of excessive moisture, or fresh concrete for that mater.  If it is soil, try some 4 or 6 mil plastic sheeting over the ground, then tape or secure it to the walls to block moisture form coming up out of the ground into your building. A fan that blows out of a vent would be a lot cheaper than a dehumidifier.  How about some pictures?  Could help tell the story.  Good Luck.