1. You need to be using the food trick to gather for resources for this to work.
2. Replace all but 2 or 3 cottages (preferably lvl 10) and non-essential buildings (stable, foundry, tavern, etc.) with BARRACKS. You can get up to 22 while still having a market, outpost, embassy, etc. You need 3 cottages for food production, or you won't be able to move your troops around.
3. Set your resource production to 100% food and 0% wood, stone, and iron. This makes all population form your 3 cottages produce food.
4. Decree NPC counties for population 3-5 times and use resources from your food-trick-gathering to make troops. As an example of how pwerful this setup is, I queued up 20k cavs and 32k swords in ONE city today... they will all be done in 92 hours.
5. Make sur eto decree gold occasionally as well since your shire won't be making much/any gold on its own.