They also said if I were to use a good test image to softproof and make adjustments to, that I should be able to copy those adjustment layers to all the images shot with that camera and to be printed with that paper and ink, and not have to tweak the adjustments for individual pictures.
Who is "they"? They re not right about much...
In point of fact, while the base curves & Hue&Sat adjustments needed may be fairly consistent, given the same output profile, they will still need slight tweaking because no two tone curves and color palette will be the same (unless it's from really similar images).
You'll need to tweak the curve and colors based on what's in the image and how the profile is behaving on the image. You also need to evaluate which rendering intent is optimal for the image and that will require tweaking the adjustments as well.
Sounds like you care more about your prints than "they" do...pat yourself on the back and tell "them" to learn how to print :~)