Tire Math based on load capacity of the tire.
Take the loaded weight of the vehicle and divide by 4.
4900 lbs. / 4 = 1225 lbs.
Each tire is supporting about 1225 pounds, give or take a bit due to weight bias front to rear, and loaded accessories.
Check the rating on the tire.
My 32" BFG Mud Terrains are rated for 2530 pounds at 50 PSI.
Divide the weight on each tire by rated capacity.
1225 / 2530 = .484, or 48.4% of the rated maximum PSI.
Adjust the PSI to that percentage of the maximum PSI.
.484 * 50 PSI = 24.2 PSI.
Adjust up or down to taste.
I run 26 PSI in my tires, and they are wearing evenly across the tread, and offer a very smooth ride. At 35 PSI, the outside edges of the tire do not touch the ground, and a piece of paper can be slid under the tread. This means the contact patch (and traction) are reduced, and the center of the tire will wear prematurely.
All in all, the best technique is still the chalk trick.