+ another one for Kool-Stop Salmon. Best grip in the wet I have had from rim brakes, and they seem to produce very little rim wear.
The only down-side is that my impression is that they do not last as long as 'harsher' pads, but still fine for most applications and in their cartridge form, easy to replace (apart from that fiddly pin). An alternative, perhaps for a very long tour, might be Kool-Stop Dual Compound - last better, which might be helpful on a long tour, and also minimal rim weat, but wet grip not quite as good.
Lewis