Yes I jump a grade as well.
For split printing Non Stain normal scene I will start at about grade 1
For split printing Pyro somewhat normal scene I will start at about grade 2.
Ralph L had some points about 00 and Ilford Warmtone not recording well.
With Pyro negs I can confirm that 0 or 00 is not great with Ilford WT .
I found this out on a sheet of film of one of the most beautiful portraits I have ever worked on.
Tibetan Warriour- photographed in a black tent with very mininmal exposure on the film. At the time I was doing 0 and 5 splits and my client pointed out to me that my blacks though detailed were not black enough. We moved up a grade and man did the print pop.
from that day on I only use 0 or 00 with Ilford Warmtone as an accent of extra tool to place tone in difficult highlights and I do not recommend splitting with 0.
This problem is very hard to see but look in your blacks, if they look a bit muddy and you are using Ilford Warmtone and splitting starting with 0 filter then move up a grade and watch some magic happen.
I disagree with most split printers on this , I only use Ilford Warmtone so maybe its not an issue with other VC papers.