I've camped there lots of times, arriving mid week. You just have to drive around the campground and find an empty spot. Except for the volunteer area there are no designated sites and really no much of any organization. Seems almost like the old west, stake your claim.
Most of the good spots closer to the show area gate will be taken, but there may be some small openings around. Depends on how big of a space you're looking for. Might be around a lot of camper trailers and motorhomes.
The last several years I've driven in my class C motorhome and pretty much just turn into the over run camping area to the West. Basically an active cow pasture complete with patties. It's generally fairly crowded but so far there's always more space..... I always bring a bike, it's a long way to the gate form teh overflow area...they have trams but I like to have my own transport.
You're in tents so stay as far away from 24 hour generator areas. My first time camping there I found a great little spot that backed to the woods but it was right along a road and across the road was a 24 hour genny spot. I do not understand why so many folks feel the need to run their generators all night, even when it's not really hot enough to absolutely require AC. especially the construction generators.... ugh! There are even some that will run them all day right up to the cut-off time in the non 24-hr areas.... why...just why? I might fire mine up to run the microwave for lunch.... or maybe for a break mid day if it's hot, but not all day and all night!
My general advice is to plan on keeping the camp site relatively simple and small, to have more flexibility...and you'll find a place.
I'm not sure yet if I'll make it this year or not..hope so.