WD40 works well. I attribute its use to keeping my bike fairly well while stored in the garage untouched for 22 years (long story) . Getting it back in presentable shape was not that bad. I still use it after the last ride of the year before putting it under a cover in the garage (unheated) for the winter. The only drawback is the film of WD40 will attract dust, etc. When it gets too bad, just wash and dry it and give it another misting.
Just an aside, but WD40 is effective for its purpose. I drive a 2000 Honda CRV. About 5 years ago, I noticed rust forming on the inside, lower edge of the doors where the outside metal skin is crimped over. There are drain holes of course, but they are fairly high. It seems over time, dust, dirt etc. accumulates down there and absorbs and holds moisture, hence the rust. I began squirting WD40 through some of the drain holes a couple of times a year as an experiment. It seems to stopped any further deterioration. Great stuff for the purpose.