I had to use a large pair of channel locks on my bulkheads.
One think I wanted to mention, when my bulkheads were leaking they were only leaking about a drop a minute. Then, I tightened them up with the channel locks, and they continued to leak. I had something I had to do at that time, and had to just leave them dripping with a towel underneath. Then, when I came back a little bit later, they were all dry. The only explanation I can see is that when they were leaking, the area between the gasket and nut (the glass thickness) had filled up with water and continued to leak after the gasket was sealed up. Then, once the water inside this area all drained out, they stopped. This was about six months ago and they are all still dry.