This may point you in the right path
https://www.sas1946.com/main/index.php/topic,13.0.html
By the way, if you want to change the default dynamic campaign skins, be them DCG, stock DGen or some mod Dgen, there are other ways to do it. For example, in DCG you can use the master.mis files in the (DCG)/masters folder, or in stock Dgen you must change the .db file in the Dgen folder