Okay! It's actually fairly simple, and there is already a tutorial right here: https://shatter-box.com/knowledgebase/android-apk-signing-tool-apk-signer/
Before exporting in Godot, you need to install the Android SDK and JDK. Then in Godot, under Settings->Editor Settings->Android, you point Godot to the paths of Adb, jarsigner, and your keystore file and user/pass that you can generate with the apk-signing tool
Your Export Settings should look like this:
http://screencast.com/t/c61FSyeynj
Also make sure you have downloaded and installed the latest Export Templates from Godot's website.
You should now be able to Export an APK with Export->Android
Next you point the apk-signer to your apk file and sign it in the second tab, then you align your signed apk in the third tab, open the apk on your android device with developer mode and USB debugging enabled and it should install!
Still figuring out how to mark this as solved....