how to add different race specific technologies to other tech trees most specifically
What do you mean?
If you want a "shared" tech you will have to define it in a Techtree.xml file located in ..Twilight\Mods\Modname\Data or ..Twilight\Mods\Modname\Data\Tech with filename of your likening for adding to default techtree
If you want to add racespecific techs you will have to define xml files in ..Twilight\Mods\Modname\Data\Techtrees