retopo Tool

I found this tutorial:

But I have to be doing something wrong. I can add the verts along side the mesh as the tutorial says 10min in. The problem I am having in the retopo tool keeps breaking outside of the mesh I am supposed to follow. As soon as it breaks I can not go back into the retopo tool. I have to delete everything and start over. As you can image this is driving me nuts!!! Can someone please help me figure out why the retopo tool keeps breaking.

I first noticed this when I tried to duplicate some geomatry and then could not get back in to the retopo tool.

Well After doing some reading it appears the retopo tool can only work with 1 mesh at a time. I may have found a solutions by clicking Shift-D for duplicate then pressing Esc to drop the mesh in the same spot. Then continuing like normal. I am still looking for clarification on this so if anyone can help. Please chime in