TDF needs to cut off the Galla and Amhara around Shire by ambushing them, raiding their 'bases'. This is a foreign land to them.
Locals only need to speak Tigrigna so to spot the foreigners from the TDF.
TDF should use captured Galla not only to carry food and supplies (adgi) but to communicate with forced Galla fighting for their Amhara Lords. They need to be told they need to lay down their weapons - there's nothing in it for them, this is a foreign land as they can see.