I used a tool available on this website, a tool that allows you to mod the fiollowing text files: party, party_templates, troops, items_kind, faction
With this tool, go to mod the file "faction" then in faction click on the factions you wish to change relations to. For each faction, there is the list of all the other factions. There are values. I believe 9.0 is positive, -9.0 negative (ennemies). Just check out some of the examples and then do the same. It is easy, simply, and you need not the module.
PS. Make sure you validate each new value before saving (this must be done and is written in the tool). There is a little special button for this.
This is a wonderful tool.