You measure first the density through the film base (developed, but unexposed) and then measure through the exposed film to get the density reading above film base+fog. This gives you density readings that you can match to your printing preferences. That's essentially what I do. I take say a zone 1 and a zone 8 exposure at the beginning of a roll from a blank card and then I can check my developing routine from time to time. I aim for a zone 1 density of around 0.1 and zone 8 of around 1.3.
I am not sure if this works for staining developers (I think Tanol is a staining developer?) as the stain can affect the paper grade so I don't use staining developers any longer with the analyser.
