Before I forget here are the general steps I followed to get TCL/TK 8.5.13 and 8.6 to work.  For TCL/TK 8.6 I had to change the actual Visual Studio 2010 project. 

Generally you have to follow the steps in readme.txt located in PCBuild of the source tree.  readme.txt references a file Tools\buildbot\external.bat which has the step by step instructions on how to build TCL/TK.  Skip the part about going to svn.python.org/external because neither 8.6 or 8.5.13 have been added yet.  So I downloaded the code from the sourceforge.net TCL/TK site.  This post explains a step that must be performed which is not documented in any of the references above:
http://mail.python.org/mailman/private/core-mentorship/2013-March/001593.html

Finally for TCL/TK 8.6 I had to change the visual studio project to use the right .lib file for TCL/TK.  Start Visual Studio 2010 right click _tkinter project then select properties.  Under the Linker/Input option set Additional Dependencies to c:\prog\cpython\tcltk\lib\tcl86tg.lib and c:\prog\cpython\tcltk\lib\tk86tg.lib

erase the old values.  Now rebuild and everything should just work (c) don't forget to manually copy the DLL files to the PCBuild directory.