Nah chest don;t work they just pop out when ressurected. I learned this when I was trying to save some Dark Mage corpses from being turned into zombies by putting them into a chest so that I could run to my wand stash and get a ressurection wand.
Sulphuric acid works but is very slow. Kenny works well while he is hungry as do other pets like polar bears or Vladimir. But they won't eat them all. Silvas wolves work. eating them yourself works. taming hordes of blinkdogs. the best method though is to have high AGI, high Int and ESP. then just run up to any necromancers as soon as they appear and kill them. I regularly clean out GC6 completely this way. Also its been a long time but if you tame an elite guard or too they get kickass fast and strong and will easily clear GC6 in no time. I had one gey get to 85 armstrength. the only problem was he got killed on gc 11 and his zombie one shotted me