The EWF influence spread through the so-called Barbarian Belt in the 800s. Lakrene was EWF by 850, Anadikki by 870, and parts of Brolia were taxed around 890. The process was for draconic groups to enter the Orlanthi lands, intimidate them and kill the leaders, then impress them with kindness. Once acclimated to draconic ways, the tribes were eventually made responsible for collecting the EWF taxes, and spreading their word, to the next tribe or clan to the west. The collectors were well rewarded in dragon lore, and in valuable goods. Thus a few great behemoth dragons slowly wended their way across the land, escorted by regional tribesmen. As a result, a wave of refugees always preceded the EWF missionaries, eventually collecting in the backwards, poor land of Brolia.
So if we think about how this might have worked, we might have some Storm Voices who can speak Auld Wyrmish riding wyverns or wyrms, some intelligent wyrms, a few other dragon speakers, maybe a dream dragon, some dragonewt auxiliaries, and plenty of tribal militia (some riding dinosaurs) annd mercenaries (Humakti, Yelmalio, etc.). That’s pretty impressive, and can quickly roll over opponents. Then you show kindness and magnanimity to the defeated and offer them something to gain. It just steamrolls along.
Until of course it stops.