My 2 cents on when tilt is used:
I first estimate the tilt angle by estimating how far below the lens my desired plane of sharp focus will intersect the hinge, then I simply calculate it by Merklinger's equation for tilt angles less than 15 degrees---the largest angle I've ever used is about 8 or 10 degrees: (focal length in mm) / (5*J), where J is the distance in feet from the lens to the hinge. It's very simple. I always rack the film plane forward or backward when focusing, so, and this is key, once I understood that the plane of sharp focus rotates, at the hinge, away from the lens with forward movement of the film plane and toward the lens with backward movement, then placing the plane of sharp focus became easier for me to understand.
Try it by applying some degree of tilt to the lens, then just focus at a vertical subject like a telephone pole until just the base of the pole is in focus, the rest out of focus. Then, while keeping the eye on the base of the pole, slowly rack the film plane backward, causing the plane of sharp focus to rotate up, toward the lens------now, successive portions of the pole, from the base and up, that lie in the plane of sharp focus will appear sharp as that plane rotates upward.
It's a lot of words to describe it, but once grasped, is surprisingly easy.