I have a feeling this is an incredibly dumb question but if you look at US and British forces they had unit flashes on their uniforms but German units don't seem to so how did they know who was who? Thanks in advance
Some German units could be somewhat identified by their uniforms. Mountain divs usually had an eidelweiss emblem on their uniform, the SS had their runes and fallschirmjagers had their smocks and different pattern helmets. Putting divisional patches on a uniform just helps the enemy's intelligence people gather order of battle info. I'm not sure we were wise doing that.
You could differentiate between Heer and Waffen SS by the collars. The location of of the eagles was also a give away. The Heer soldiers had them over their right breast pocket. The Waffen SS had them on their left sleeve. Later in the war the Waffen SS had camouflage smocks and helmets. Oh yeah speaking of, the Waffen SS had the SS runes on the right side whereas the Heer only had the tricolor shield. As far as individual units the Waffen SS had cuff identification for a while but that went away. Hope this answers your question
I found it interesting that if you had served in One SS division, and was moved to another, you could wear both unit's cuffs. Like LAH and das Reich, both.