1- First use the two wrenches to loosen the jam nut from the flange nut.
2-Remove jam nut, flange nut and dog washer from the cone/plug shaft and set aside. Some brands like the old Wilcox Crittenden seacocks did not have "dogs" on the washer. Many a tapered cone owner, myself included, have dropped jam nuts, flange nuts or the dog washer into the bilge during removal or re-installation. A wise man once suggested to me to wrap a towel around the base of the seacock when removing the pieces. This prevents the old "bounce & slide" disappearing act. On some boats if you drop a part they are gone forever!
3-Use handle to move valve and the cone/plug will pop out.
4- If the valve was stuck a light tap on the nut end, with a hardwood mallet, will almost always free the cone from the valve body. If you do not have a hardwood mallet just leave the jam nut 90% on and tap on the nut. This will prevent you from damaging the threads on the cones shaft. DO NOT beat on it.
5- Use a good grease cutting solvent & a rag, I like odorless mineral spirits, to thoroughly clean the inside of the valve body.