I have been building Squeeze+Trinity live cd's for some time. I use my own scripts mainly as I found official Debian-Live quite difficult to get exactly what I wanted.
Remastersys is really good. I use it sometimes. It is designed for stable; a squeeze version is available but you will need to modify the current version.
You need installed live-initramfs 1.177-1 (get from snapshots.debian.org) and grub-legacy.
http://www.remastersys.com/forums/index.php?PHPSESSID=3sugievt9bg9or5p0nhlbr...
is worth reading.
In addition you need to hack the script live-initramfs script "15autologin" (I posted details on the above link) and remastersys-installer.for Trinity to work properly
If there is any interest I could post here more details. My Live ISO (700mb) is available on request, would appreciate some testers!.