https://www.coh2.org/replay/51523/how-to-defeat-the-sim-city-strat-cancer-regiment-wehrmacht
I made this guide long time ago FOR WEHRMACHT... it is still pretty usefull, but cant promise its efficiency in cheesy 3v3/4v4 sry.
If you play OKW with randoms, there is sadly nothing you can do vs british sim cities who get hard camped with vickers, at gun, PIAT blob etc.
You need to play with an arranged team in such situations: 1 can bring some stukas out to kill the enemy support guns (HMG, AT gun) who camp the sim city (NEVER use stuka vs emplacement, it's a total waste if the enemy has access to brace in the moment the rockets land)
Others can get puma, luchs, LeIg out so that you can deal with everything in mid game.. in case you have a good teamwork. As soon as your indirect fire did a good job vs the support guns, agressively used inf can tear down emplacements aswell.
But again, playing vs sim city cheese in randumb mode is total cancer and a waste of time.