The older, unlined
coach bags can be dunked and they come out great! You can even turn many of them inside-out to get the entire bag nice and clean. You need to use a dye and fragrance free soap like Ivory or Woolite.
I soaked it in woolite and warm water for about 45 minutes, then rubbed it down with a soft cloth and gave it a vigorous bath, paying special attention to the dirtiest areas. Then I soaked it in warm water for about a half hour and rinsed it well.
I let it drain in the sink for a bit and then stuffed the bag with old towels to reshape it and let it dry on another towel for 24 hours. Then I took the towels out, rotated it periodically and let it continue to dry over the next few days.
When it is almost completely dry you should apply a leather conditioner. Most Coach bags respond well to Apple Leather Conditioner that is available at Burlington Coat Factory stores. But occassionally you find a bag that needs more intensive leather care. In such cases I use a product available from a local equestrian riding store called "
Leather Therapy - Restorer & Conditioner" that claims to be "a blend of rich, replenishing oils formulated to transform dry, hard leather to original flexibility".
The label says that it will NOT darken leather and that it will work on both hard and soft leathers. It is also supposed to inhibit mold and mildew!
Whatever leather product you decide to use, be sure to check the label and contents. You don't want anything that contains petroleum distillates, silicones, waxes, dyes, or perfumes/fragrances.
The only problem with the Leather Therapy is that it is expensive. The riding store only had big, 16 oz bottles that cost $26 but I have already used it on a few bags and it has worked well for me so I am okay with the price. Here's a link to a site that sells the stuff online (NMA):
http://www.leathertherapy.com/index.php?main_page=product_info&products_id=190
After the conditioner dries you need to rub the bag with a soft, clean cloth to buff it. If the leather still doesn't look good you may want to repeat the conditioning process. When the bag is almost done, use wenol or brasso or other metal polish to shine up the hardware. Try not to get the metal polish on the bag but if you do - just quickly wipe it off with a damp cloth and it should be fine.
There are other products and technigues for different issues and bags. Lexol leather wipes, alcohol to remove ink marks, etc.
My advice is to look for an inexpensive "test bag" that isn't in terrible shape at a thrift shop, garage sale, ebay, etc. Post pics of it in the authentication thread first to make sure that it is genuine because you don't want to invest all this work in a fake, and then try restoring it! Good luck!