The quickest way to extrude, he says, is by holding CTRL and pressing the right mouse button where you want to lay down your vertices so you don't have to adjust the geometry much.
When you're done with retopology, you can simply redistribute the vertices using the Relax Slide brush. It relaxes the geometry without deflating the volume.
If you found this tip useful, see how you can sculpt ears, create holes, use Grid Fill in Blender 4.5 LTS, and more on the artist's X/Twitter: