Fine cloth-backed sandpaper is best, cut into 2"x4" rectangles. Get the inside of fittings too. Of course if you are lost on a desert island, some beach sand and spit in a hanky will work. :-)
I'm not really a human, but I play one on earth.
flash japh
Comment on Re^5: Always be learning - how a leaky pipe made me appreciate Open Source (OT) Sandpaper