Is this a hang on back or drilled bulkhead? Are you sure the leak isn't coming from the bulkhead i.e. A rubber seal not seated properly or a cracked bulkhead? Did you have to force anything or was it fairly smooth treading it?
Teflon tape usually is enough to keep drips from a bulkhead drain from leaking. Not sure why you only threaded it half way though, if it can be threaded more onto the bulkhead I would try that first before adding more tape.
If you haven't figured it out yet I like to BOLD links :P