HiCustomer welcome to Just Answer!.
The Slim Jim will work, but it involves a little skill, a little luck and a lot of patience if you haven't done this before.
Note that the Slim Jim has cutouts that are different on the two sides. One side will push better, the other will hook and pull. The bar is flexible, a big plus.
Start with the tool pretty much straight and just slip it down between the glass and the door about 6" out from the rearward edge of the glass. As you move it about, up/down/side/side, watch the door lock knob inside the truck. Tilt the tool so that the business end is spending time in the door latch area, about 20-28" down from the door top. If you see the knob move at all, you're near the link that controls unlocking the door. Concentrate on that area.
Once you're frustrated with the results as-is (lol), pull the tool out and bend it a bit so that it will sweep a different area inside the door. You'll probably wind up bending it both ways, so it doesn't matter at this time how it's done. Repeat.
With no results, pull the tool out and rotate it 180 degrees (no rebend) and insert it again. Repeat. This sweeps yet another area and uses the opposite side of the tool.
Next would be to bend it opposite what you've got now and reinsert.
Then rotate (no rebend) and repeat.
Somewhere along the line, you'll see movement of the lock button... like getting a nibble if you were fishing. Try to cultivate that nibble and note whether the lock button moves up or down while it's being touched. You may have to reverse the tool to the push or pull (hook) side for the results you need.
Try to avoid going crazy in there! I've seen some damage done that requires panel removal to reconnect links and such when someone gets animalistic with these things. But then again... they WERE animals. You'll do better.
Take your time, try the other side of the truck or back doors if it's so-equipped. The linkages that will be useful to you are all in the rear 6" of door volume, so concentrate your efforts in that area.