Yesterday I took the 5Diii to an allotment with me, the in camera HDR was pretty ineffective (like it is in all cameras I have tried), but merging the same three shots in Affinity, it works well to increase detail in shadows, and also to increase detail in places like the top of trees against a light cloud background (light cloud as in bright, not little cloud).
That is not going to help though with 500 photos to process.
I also set a custom picture style with sharpness at max (the 5Diii's JPEGS are soft anyway), contrast at max, saturation at 75%, and using spot metering well below the skyline, and that helped a lot, but of course the sky detail was lost.
Not as good as a merge, but not too bad.
Out of your potential 500 shots, how many of them would you end up using?
Possibilities could increase if it was a lot less then the 500.
Any of the solutions suggested will have a varying effect depending on what is actually in the picture you want to see.