I used the ilford ilfosol 3 and the concentration was the economy solution (I'm out of the country and can't remember the actual dilution.
The 'push' rule that I came across could've actually been wrong it was a passing rule I saw on the internet that for every stop you want to push, you increase development time by two minutes.
I think this is part of your problem in the development stage. Ilfords own documentation has no push processing recommendations for Delta 100 and Ilfosol3.