Before starting to take the mesh apart, let's create a layer, so we can jump back to our original work easily. Layers are also very useful if we have to do an object in several states, like for example intact, damaged, and wrecked. We can add a layer for each and quickly switch between them. Also if we want to try out something, we can do it on a layer without losing the original work.
Layers are located under Tool | Layers. We can add a new layer by clicking on Tool | Layers | New with our model at its highest level of subdivision. So to add damages and finest details, make sure to step up to the highest level of subdivision before adding a new layer.
If we create a new layer, it automatically switches to record mode. This will record everything we do from now on, to that layer. If we click next to the record icon, we can toggle recording off. Out of recording mode, layers work very similar to Subtools, having an eye icon to toggle the visibility. Only one layer can be in recording...