As for the trains, when I'm over there I tend to grab the luggage rack support as it is too high up for most Japanese, or I grab the hand rings supports that attach to the ceilings. One definite advantage to being tall gaijin :P

I have only ever seen the gel based hand washes, who makes the water based ones?

Oh! Good suggestion on the sleeve!

As for sick people in Japan, depressingly few are so polite about spreading germs. I cannot tell you how many students come up to me when I am at my desk, and literally standing right over me, no mask or anything, report that they are very ill. Distance, please? One class I taught required me to stick to a whiteboard–immediately next to which was a student, clearly ill, who constantly sneezed an coughed without covering his mouth. And let's not get into riding public trains, where you usually have to stand up and grasp surfaces that hundreds of others have had their hands on that morning, and the people with colds, mostly without masks, are crowded and shoved right into you.

One thing that helps me a great deal: alcohol-based hand wash. I hate the gel stuff–I have no idea why it's predominant, it's icky and leaves residue–but I found and bought a large cache of water-based wash, and it's fantastic. Seriously, I got a lot fewer colds after I started using it regularly.

Another good technique: use your sleeve to satisfy an itch on your face. Your sleeve is a lot less likely than your hands to carry an infection, and let's face it–most of the time, not touching your face is very hard to do.

Also all good suggestions.