This manual, as its title implies is focussed on the farming of snails covering the topic in great depth.
(click image for full story online)
There is, however quite a lot online on the marketing and processing of snails in a number of different sources. To have a look click this link and you will be assisted to make a google search which should give you a good start to finding useful information.
Anyone with information to share can email me here. and I will add links here.