Best way to manage string resources in Android

Question

I am recently learning Android app development and met string resources. Then I start thinking to hold some warning message in resources XML for Toast.makeText, so that I can utilize the native i18n feature. But then I find that even with a small app, there might be many messages and can easily drain the resource name.

Here is my question:

1. Is using string resources to hold error messages is a bad idea?
2. How do those huge projects manage those string resources? Load over network or something else.

I found many posts only talking about how to use the string resources (with R.string.foobar), but not for experience sharing. Please share some of your experience, thank you in advance.

ps. Is there any way to separate resources, like an XML file for this activity and another for that, etc?