I used this guy’s guide.
Overrun at wave 369 but got 31k points in the end.
Note: I played the old downloadable version of the game from the official mud and blood website, but the strategy is applicable in newer versions.
Another Note: My bunker apparently teleported from the center of the map near the trench to near the bottom left in front of the 50 cal. I don’t know why.
The strategy is to use gunners and .50 cal guns to mow down infantry and light vehicles while you micro an engineer to take out the tanks with mines. Meanwhile, snipers and a signaler do their magic at the bottom corners of the map in camnets protected by light armored vehicles (Jeep , Halftrack) and sandbags. I like how he replaced conventional Anti-tank options (ATs, bazookas) with a single engineer in a pillbox.
The advantage of this strategy is that you don’t use units with unpredictable explosive attacks(mortars, bazookas, ATs), thereby, eliminating the risk of blowing your soldiers or structures up when enemies get too close.