1- Open your mod in the toolset, then open the "modules" folder with Windows Explorer(if under Windows, obviously). You will see a folder, "Temp0", which is holding the resources of your mod.
2- You can instantly delete any number of resources you wish in the folder.(make sure you know what you're doing as you can blast everything this way)
3- Go back to the toolset and save your mod.(you may need to make a small change and revert to be allowed to save)
Kato