Ok, although you haven't been hearing about this, my rudder post packing gland, very similar to a main shaft stuffing box, has been leaking. I'm not surprised as it looks as if it hasn't been adjusted in the thirty years since it was installed.
I was going to repack it but there was still a great deal of adjustment left. But here's the thing: the tools you can purchase at marine stores are absolutely worthless. They bend and warp and don't have any use aboard a boat. But the right tool is available - and it's from one of my favorite tool companies, Rigid.
You never want to use pump pliers or pipe wrenches on a stuffing gland. The last thing you want to do is chew up the relatively soft bronze fittings. Once you do, you'll never be able to use a real proper wrench again without removing whatever shaft you're dealing with.
So, I've been struggling with this dilemma until I found these wrenches. They are perfect! Boy, oh boy, the job was done in just a few minutes rather than the hours struggling I've done so far trying to move the nuts.
So, the first job is to loosen the locking nut - with this wrench adjusted properly, it was a couple of taps on the handle with the hammer and presto! All loose. Then I removed the actual packing nut and held it up above the whole fitting. Next, I ran the nut down the threads as far as I could and back a couple of times to clean the threads. When doing this, don't rush. Go a little way, then back off - there should be water coming through the packing material that helps wash away the salt and corrosion.
Finally, I schmeared lithium grease all over the threads and re-ran the locking nut back down. Then I put some grease on top of the packing itself and ran the packing nut down to a little over hand tight so that no water was coming out. Remember, the rudder shaft doesn't really need a lot of lubrication as it doesn't spin. The main shaft has a little different adjusting procedure.
The last thing to do is to snug the lock nut up against the packing nut and Bob's your uncle. It will take you way longer to read this than do. Repacking only changes this in that you have to remove all the packing letting in a considerable amount of water (not a dangerous amount, though) and replace with whatever kind you like - I like the graphite impregnated stuff.