Different types of weather seal work great, but try to not to totally seal box, condensation will be worse, I keep a couple of small weep holes in the bottom, it keeps inside condensation down to nothing, also I do put a small screen over the holes to keep out bugs from nesting inside.
You know, I don't think I have ever seen condendation in my Cam Enclosures?
My Pistol Cases have foam that completely fills the inside, I cut-out for the PIR, Cam, Batt, etc. but the enclosure is all foam otherwise. I wonder if this is like one of those Cold Cups around a beer can and stops condensation!
Some buildings have "Anti-Sweat" pipe insulation on pipes that might drip on sensitive equipment, etc, You may have even seen sweating pipes in your basement, especially if you have a well. If this is a problem, insulate the pipe and no sweat.....
My cams all have tight packed foam too... and now that you mention it I can only remember one time that the inside of one of my enclosures was all fogged up. We had some extreme night to day temp variations that week so that probably caused it.
Maybe the foam reduces the amout of air inside the box and that helps reduce condensation too??