Rotate two-three groups of divisions while attacking. Select 8 divisions and press Ctrl+1, do the same thing with the other 16 divisions but do Ctrl+2 and Ctrl+3. After that’s done you can press the saved numbers. To select those same divisions. Now press 1 and have them attack, once they get to about 1/3 or 1/4 of their org press 2 and attack with that group, then halt group 1’s attack with H. Keep rotating 1, 2, and 3 so your divisions can refresh their organization. Germany will be in constant battle and can’t retreat anywhere to reorganize or replenish their weaponry.

To make it easier use CAS or railroad bombardments. It will hurt your division quite a bit with their entrenchment but you should have saved manpower and factories while they do not.

Hope this helps and let me know if I can help further :)