Basically in meteor package,js you should depend on npm package with your custom styl files and of course on stylus npm package. Then in your app you will be able to easily import your styles from .styl files included in npm dependency. (In your main .styl file place @import 'my-file-name-from-npm-dependency-package' you can ommit .styl extension)
‘compile-stylus.js’ plugin will compile it all to css on your app startup.
Meteor is very helpful in the front-end work too : )
Meteor + Stylus + good grid system (like for example Jeet) is a powerful toolset for prototyping.