Been using the Wilderness Systems HD cart on my Bigwater 132 PDL for about a year.  In parking lots and boat ramps I pretty much have the system down.  Yesterday I launched off the side of the road on a slope at a culvert.  Yak went in the water just fine as gravity did its job.  Getting the thing out after fishing was another story.  Had a hard time finding the cart in the muddy water underneath the kayak and was up to my elbows in water trying to get the strap around the cart crossbar.  Lugging the thing up the slope was pure entertainment.  I typically secure the strap to the drive.  In this case it would probably been a whole lot easier leaving the drive out as well as all my gear. 

Monkeyfist and LawyerBob showed up after my comedy routine.  Monkeyfist had a home made cart with a rope that he basically just threw under his Hobie and then pulled a rope attached to the cart....looked a whole lot easier.  He also used it on LayerBob's stripped down Salty and it seemed to work but not as easy as on his Hobie.

I am looking for any tips, ideas, and pictures of how you wrestle your kayaks in the wild and in particular how you attach your carts when launching at unimproved/improvised sites.

It might be more of a launch issue and less of a cart problem. I keep a pair of pruning shears in the truck for spots like this.  Five minutes of work and you would have a much improved launch your cart might work better at.

When launching and landing I skipped the cart and parked my truck on the side of the road and just slide it in, and dragged it up. I cant imagine trying to get a cart under the kayak while still in the water

Never been there, but looking at the photo that's what I was thinking.

Assuming there aren't a ton of sharp rocks, I'd offload what I can, secure the other items to the kayak, and then tie a long rope to the nose of the kayak and pull it up w/o using any wheels.

If there are a ton of sharp rocks that don't preclude cart use, I'd do the same thing but stop just as soon as the stern is out of water... then slap on the cart, and resume pulling.

If I used this type of launch w/ any frequency, I'd consider a pulley system to decrease pulling effort.