RegionFill is a very simple plugin created to automate process of filling WorldGuard region with defined blocks. It not requires a player to execute command and you can run it using server console and any scheduling or scripting plugin. I'm recommending you ReActions, of cause :)
In this video RegionFill used in bound with ReActions plugin.
If you going to add some automation process to your server (for example to clear quest area, build something.... etc) you can use this plugin (and my other plugin ScLoad). We used this plugin in bound with plugins Citizens (using Quester), ReActions and you can easy use this plugin with any plugin that supports command execution.