Using policy to deploy an extension or Chrome web app is the easiest and most scalable method. This is the recommended method for pushing extensions, as it does not require the CRX file to be on the machine. It must simply be available at a given URL.

To use this method, set the policy to "force install" the extension, as described here.

Force-installed extensions are added to the master_preferences file that lives next to chrome.exe. This means that the CRX file can live anywhere, and the bits don't need to live on the target user's machine and don't need to be packaged into any installation script.
See support.google.com/chrome for additional information