Guides from a Mesh

Make guides from existing edges instead of drawing them.

Guide from Edges / Hard Edge

In Edit Mode, select edges (an edge loop around a wrist, the rim of an eye) and press Guide from Edges. Hard Edge does the same and keeps the edge sharp under a Subdivision Surface.

Protect Selected Loops

In Edit Mode on a result, select a loop you like and press Protect Selected Loops. The next remesh keeps it where it is.

Guides from Selected Mesh

Start from an old retopology or a cage: select it, then Shift+LMB the mesh to remesh, and press Guides from Selected Mesh in the Expert section. The new quads follow the cage's faces.