So the 2.8-4-5.6-8-11-16 second sequence gives you a factor of 1.4=sqrt(2), which is half-stop spacing when used as times. When you're printing at lower grades you need bigger steps and when printing at higher grades, you need smaller steps to achieve the same shift in tone; the reason is the changed slope of the paper's response.
You want the total exposure for each bit of paper to be the number from the sequence, so (assuming you're doing the covering-up thing) each exposure is the difference between respective steps: 2.8, 4-2.8=1.2, 5.6-4=1.6, 8-5.6=2.4, 11-8=3, 16-11=5, 23-16=7, 32-23=9.I think I get the gist, but with linear intervals, I set my timer on the time, then slide a sheet from one side of the print to the other. How do you do that with fstop printing? If I added 5.6 seconds on top of the 8 second, that would give me 13.6 seconds. I would have to cover that 8 second portion right?
* the numerical sequence looks familiar only because it is a geometric sequence with factor sqrt(2). The numbers for full stops on aperture match the numbers for half stops on time because aperture area and therefore exposure varies quadratically with respect to f-number.