If you want to do it faster you might want to change a few things.

If you put all your troops in the western most province of Franken they'll all get moved close to that province, but all nazi troops will still be in that province -> you can (in theory atleast) cut them off easily and have fewer troops to deal with.

If you have more then 24 troops in a group you get a less of a buff, so might want to split them into 2 groups.

ok thx for the tip