I usually print stripes of the image.
Lets say I would want a 24x36" final print of a tricky image, I would probably print 2 or 3 stripes of 24x3" of the more potentially problematic areas. To do that I would create a 24x3" paper size, set Lightroom print module to "zoom to fill" and position the stripes by dragging the image. Quick, simple and provides real size crop stripes good for checking detail, sharpness, noise, colour accuracy... everything.
Best regards.