ZBrushCentral

sculpting with symmetry on 3d scanned mesh

Hello and apologies for this newbie question.

I want to edit in zbrush 3d scanned meshes (faces) which by definition are not perfectly symmetrical. My question is as simple as this, how can I sculpt with symmetry on these meshes, in other words can I force symmetry axis on an imported imperfect mesh?

I am well aware that zbrush may not be able to sculpt symmetrically on a mesh that is not perfectly symmetrical itself, so I am wondering if this is even possible in fact. But I guess someone must have thought this through in the past? I would hate to use another software such as a reverse engineering soft just for that.

Or as a workaround, should I project my mesh on a symmetrical subtool and take it from there?

Thank you