Jeff pretty much says it to the tee. White can be easy or hard, it just depends on the conditions of the paint and the actual color of the white. Where it was built also can change the variance in the same paint code. For example Honda Odyssey, has 1 white, built in two different plants. When I mix paint I have to check the vin for the build so I know which white to mix.
On Topic... I have mix feelings about T2F, I have seen very nice work come out of 2 of there shops, and at the same time I have seen what "looked" like single stage black on a brand new vehicle from Grandview. And the Dublin location told me there work on a door seam was a factory seam bead. Me knowing the inside of the door was fixed when I inspected it I asked them to check the other door for comparison. What it was, was unfinished body filler that was painted over.
No one shop is perfect though. My employee used to work for Achbach and has told me the horror stories of hack jobs that have left that shop.