Hi Bill
For a six cup, I add half a broken up shell to the grounds in the basket, and perc as normal.
I have , in the past, made cowboy coffee. Where you don't use the basket, and put your water, coffee
(a little less coffee) and the broken shell into the pot, bring to a boil, remove from heat, let sit a few min, then pour. I poured threw a tea strainer so maybe I took the "cowboy" out of it! Very good from what I remember.