ff103, I regularly remaster like you propose & what I found that works for me is;
1. create a guest account if you don't already have one
2. disable autologon if you use it
3. log out of user & logon as guest
4. run the bleachbits, umount -a
5. run your mylivecd command from a root terminal.
here's my last mylivecd command line;
mylivecd --nodir ^/home/john --gzip kde64-01.2012.iso
You will end up with your user account, but no files. I use this if I need to reinstall & preserve my user files which are on a separate partition. (the --gzip command is not necessary, just runs faster)
Works for me.