I've owned my cerf tote for about 6 years now and I ADORE it! It's my go to bag for day or night when I have some extra "stuff" I need to lug with me. It's perfect for work as well! It's loosing the shape has always bothered me and I used to fuss with tissue but have since found these bag inserts:
http://www.bagavie.com/
Here is the blog where it explains about how to use with cerf tote:
Your Bag-a-Vie, your way!
Chanel cerf tote.....gorgeous bag, soft leather! How do we keep it looking firm while not in use? Depends on you! If you are very particular and would like to keep the corners as firm as possible, use 2 MEDI stacked horizontally one on top of the other. This will support the body while keeping the base nice and firm. Not that picky and love that "broken in" look? Use 2 GRANDE side by side vertically. Keeps the bag firm and makes storage a breeze! Your Bag-a-Vie..............for the love of handbags!
I have been using them for about 2 months now and they are just amazing!!! The bag is perfectly formed and stays "sharp", if you know what I mean. I can't say enough about these!! Love them!!!