I have "too many" lenses, many more than those I used in the past 12 months.
So far I only sold obviously redundant lenses, and always via a shop, preferrably one that will give me the cash after a short check (example: FNAC, a big retailer), alternatively one that pays me once the lens gets re-sold (dépôt vente in French; usually small shops specialized in second hand gear; e.g. many places around Boulevard Beaumarchais in Paris).
I am psychologically ready for any discussion about the lens condition and price with a professional, not with a random buyer.