I'm afraid that there's no real alternative to doing at least some testing.
But eventually. No need to rush.
Remember, we are not testing the response of film alone; we are testing how our particular system, methods, skills and print preferences and even our choice of subject matter perform. It's possible that one person agitates more or less vigorously or their darkroom room is slightly cooler or warmer than the developer, or their eyes perceive shadows differently from the next photographer. The local water may be more acidic or alkaline. One photographer may start the timer after all the liquid is poured in and another may do the reverse. For all I know, the brightness of our ground glasses may influence how we choose to expose. Bellows may have flare that helps to lift FB+F and improve shadow response, allowing us to reduce film speed less.
Most people seem to find that they more-or-less halve the film speed and reduce development by about 20% for normal development. There are similar common findings for plus and minus development. All this assumes a fairly standard film such as FP4 or Tri-X and a fairly standard developer, ID11 or D76. I believe that these developers are used when manufacturers determine film speed.
These methods were all devised in the days of single grade papers where careful matching of negative to paper was essential. I believe the same is true today for alternative processes (has film been promoted to "Alternative" nowadays?) such as Platinum printing.
As Stephen pointed out and illustrated so elegantly above, the scanning process is flexible enough that as long as the image data are captured on the neg, they can be retrieved by software, although naturally, a controlled negative will make life much easier. There's little need to agonise over hitting exactly 0.01 over FB+F and a little extra density in the shadows will do no harm at all. The great vice is excessive density in the highlights, because scanners fail to penetrate excess density and highlight detail will be lost. There are ways of reducing density in negatives, but they all carry some risk.
I've found that when explaining to novice photographers why we do this or that thing, the explanation always seems to be that it will make the next stage much easier.