After some experimenting I settled on fine steel wool with oil or diesel for lube. Then I scrape off the chunky stuff with either a fingernail, screwdriver, or razor blade. Then steel wool again.
I only attacked the left side of the handlebar. I wasn't trying to capture the turn signals so they're mostly blocked, but you might notice that one of them things aint like the other. Kinda funny, a shiny left bar and shiny right signal. So weird that the left bar clamp is fine and the right is all fuckered up, but the bar and bolts are about the same on both sides. Monday chrome vs. Friday chrome?
I also found it strange that the rear wheel is way more rusted than the front, and the left side of the rear is worse than the right. I woulda thunk that chain lube fling-off would have given some protection, but it appears to have eaten the chrome instead. Or maybe dirt and stuff flinging off the chain damaged the chrome leading to faster rusting?