I saw a really clever technique in a video by Ryan Kingslien and had to try it out. Instead of sculpting on top of a flat featureless basemesh I made a quick wire armature with zSpheres and then used the InsertSphere brush to add "lumps of clay" that I then stretched and deformed into the different muscles and big forms. Essentially emulating how one would work with clay in real life. It's a really obvious way to work when I think about it, and the tools have been around since zBrush 3 so I have no idea why I never throught of it before.
Here is the video I mentioned by the way:
