It's not that difficult at all. Position the tool you are using (parting tool) to the same starting postions as your threading tool. (Be sure to run the same RPM and feedrate as the threading tool.) Now just use the same threading cycle you used to thread the part. You don't have to make as many passes as the threader, it's up to you. It would probably be easier for you to use a smaller Z minus number in the program to start with, and then keep adding to the Z minus in the program until you are happy with where the tool is pulling out.
Hope this helps.