When you start put all of your men in one army and set them to garrison Konigsberg and Ermland-Masuren. Build factories in the Western states that won't rebel once you oppose Hiter. Start training a bunch of Panzer divisions and don't set their deployment zone. I'd recommend going down the Army and Airforce national focuses but the important thing is to wait until some of the Panzers are ready to deploy before selecting the oppose Hitler focus. In this time I'd recommend getting the a tank manufacturing company and generals with your pp. If you're going for the achievement that includes the German Empire conquering a Caribbean island it's also best to start your wargoal on Haiti, Cuba or the Dominican Republic now before you switch to the Empire.

When you finish the oppose Hitler focus the Fascists will rebel in Eastern Germany and the Southern state in the part surrounded by Poland. Here's what to do straight away:
- Make an army out of the units that spawn in Western Germany and assign them to the Fascist line,
don't get them to attack.
- Assign your airforce to the Western Poland area, over where your armies were garrisoned.
- Form an army with the forces that were garrisoned in the states surrounded by Poland and make a front line on the southern state that is opposing you. Set the army to aggressively attack and set the frontline to the bottom of the state.
- Have your navy patrol the lower Baltic sea
- Deploy those Panzers you had earlier, assign them to a new army and set the front line to the Central German divide and wait for part 3.

The front line through the centre of Germany shouldn't see much action and you should easily wipe the forces from the eastern states surrounded by Poland, by the time I fully occupied Ermland-Masuren I had 12k losses and the Reich had 126k losses.

After this assign your army from that eastern part to a small front line in the North and have them push to Berlin, I found it best to continue not giving an offensive to the army that is already there and manually having them assist the attacking army until you get to Berlin. When the attacking army gets there assign those Panzers you deployed to their army. Also make sure your air forces are now concentrated here.
After the fall of Berlin you continue in two ways:
- assign the attacking army to cut off the Reichs southern part and then have them attack that area.
After this it should be easy to have the entire army push through the remaining areas in the north.
OR
- Redraw the front line and keep pushing small sections of the North, if you can trap fascist forces in the two areas that split off around Poland you can get a bunch more enemy casualties that way. After that push down from the North to Bavaria or push from the bottom part of the main front line through to the east.

Congratulations and long live the Kaiser

Protip: Don't attempt to bring Wilhelm back from the Netherlands straight away, wait until you have a strong army otherwise the Netherlands will not allow his return. This isn't vital since you can restore a different kaiser instead but if you want Willy back then you have to have ~40-50 divisions for a guaranteed acceptance from the Netherlands.