Snail mucous has many advantages, what is the best way to extract it without changing its composition?

Collect the mucous from a sheet of paper and dissove it with ethanol of various pecentages.
Best

Let it walk on the absorbent paper, such as filter paper used in the chemistry lab, then cut out the snail tracks and dissolve them in PBS. 

Understanding the stability of the substances you intend to study after collection is important. Are there key compounds in the mucus? Are they stable at neutral, acid, or basic pH? Are there compounds that might transesterify if an alcohol is used as a solvent, or will water hydrolyze any compounds of interest, thus making a polar aprotic solvent better for collection purposes? How labile are the compounds of interest over time? Is it appropriate to store the mucus and/or target compounds at lower temperatures shortly after collection, or does the mucus degrade and affect the stability of the compounds?
To summarize, you have to know what you're studying so that your studies have reliable results.

Similar to collecting mucus on the paper, collect it on a moving surface, so that the concentration of mucus can be increased at a particular place.

Secondly, the silica or some other inert material powder can be spread over which snails will crawl. The powder can be collected later and used for mucus extraction.