Doors can be a B--ch, sometimes they're just screwed up and other times jacking one corner or another can help (and adding shims once you find out what helps)
The computer fan would probably help, unless you wanna actually WORK inside - I have a 20, 2 40's and 2 40 hi-cubes. I built a steel framed 24'x24' roof over the 20 - between the roof and a few trees, that one NEVER sees the sun. Any time of the day or nite, I can walk inside and it's the same temp as outside.
The 2 standard 40's are storage, some of which does NOT need extreme temp swings - the two hi-cubes will be welded together parallel to each other, with connecting areas between and a bridge crane in one side (the weld area) - other side will get tools and machine area. Eventually a 60' square shop will be built around those two.
With ALL the 40's, I've measured
inside temps with an IR gun at over 140 F during direct sun, when the outside temp was a bit over 60. (doors had been closed, but doesn't make a lot of difference)
My solution isn't quick, but necessary for me - I still need the security aspect due to the general neighborhood AND one neighbor in particular (not to mention bugs, possums, raccoons, bees, birds, etc - also, it's gonna be a while before I can afford the REST of the plan (roof over 2, 60' square slab and shop over the other two) so I bought greenhouse vent kits and am (slowly) in the process of building secure bezels for both the shutter fan AND the linked louver panel for inlet air, ALL of which will have welded bars over the outside plus screening for the other critters - all these will be on the leeward sides of the containers (our hill gets quite a bit of "horizontal rain") and be automated by temperature.
I have 20" fans hanging by the doors (ceiling height) facing out at the moment, NOT secure/NOT bug proof and only mitigates the temp within about 15' from the door, whether blowing in or out
The greenhouse kits were about $350 each, include 16" shutter fan and 24" motorized louvers with controller. Not cheep, but doable sooner than $80 thou for complete pole shop/slab. Now all I gotta do is keep from losing that "round tuit"
... Steve