I (AD), was eventually able to update an English version from a French version. It worked quite nicely actually! I found the French diff on top of the English text box worked quite well, and enabled me to quickly zero in on what needed to be done.
But here are some improvements.
The caption at the top that says:
Edit: Alain Désilets, es
Comparing version 1 with version 5
Should really say something like this:
Update "Alain Désiets, es" based on "Alain Désilets, fr"
Changes that need to be reproduced in Spanish are highlighted below.
Alain or Seb should be able to do this next TikiFest.