Ok, just wanting to know the right way. I have removed 8 old rings of the stuff, which seems to be a lot. They may have been just 90° butted together, hard to tell now.
I am heartily sick of water in the bilge so will do it the best I can while the boat is on the hard!
I just bought some PTFE Flax packing. There is supposed to be enough in the pack for one shaft, but at best it would do 4 rings so I bought 2 packs. After I got home I noticed the pack said to use 'syntel' shaft lubricant when installing, so another visit to the chandlery before I can proceed!