Can I suggest you purchase a large frisbee or similar then cut a hole and slot in it so that it will slide over the stub axle and create a shield to the brake disc, you could affix with some long velcro fed through each side of the outer edge of the frisbee running across the outside of the disk top and bottom. Then you will be safer when washing of the springs and getting rid of the muck.
I would also consider switching to Lucas Red'n'Tacky grease, which I have been using for over a year, it is very hydrophobic and is extremely good on sliding surfaces, I find that it lasts at least 50% longer that other greases in the king pins. I have found that to get the best out of greasing the pins you need to start on the top grease nipple and just pump and pump until grease starts to come out of the bottom, this can take a while and is not easy. Then a few pumps on the bottom nipple.
