hi
this should help you:
https://technet.microsoft.com/en-us/library/hh825096.aspx
you can create the *swm files with winreducer.
you can do that after removing your stuff, and getting to the "save in wim file /save in iso" window. select the save in wim file window and enter an splitt size
or when you got an finished iso, start winreducer goto START -> Tools, at Tools goto ISO and do the same steps as mentioned above