Yes, it's MOSTLY that easy. Diafine was probably geared for Tri-X, but other films can do well in it. Lots of folks say Plus-X looked good in it, but I never tried it. Pan-F works at EI 80, but I did not like APX 400 in Diafine.
You can tweak the results a bit by adding/subtracting a minute to the times, but don't expect big changes.
They say on the box package that Diafine won't work well with some of the lower ISO films. The box also says you can get EI 1600 out of TX, but I get 1000. It gives TX a bit of the old look: contrasty, gutsy negs with some grain.