Butzi gives a very clear summary of the testing process one can use with XTOL. The work that Kodak did when they prepared the XTOL data was superb, and a photographer today is justified in a new form of calibration.
Instead of assuming there is no data for either the film or developer, and starting from scratch,
assume EKC gave you great information and YOUR job is to see how your exposure meter, thermometer,
and other variables, differs from THEIRS !
Here is a neat resource, a German Kodak XTOL pdf still online,
(the original edition) with both full dilution data AND a remarkable set of curves, at the end of the document.
While there WILL be some variation with constant agitation,
this is well worth a look. I have never had problems with 1+2 dilution, and 1+3 might be very good with a JOBO.
http://wwwfr.kodak.com/AT/plugins/acrobat/de/professional/xtolEntwickler.pdf