Get a bottle of 303 (made for restoring vinyl dashes and such) and submerge the hoses in it for a few days or so. I use it all the time on rubber plugs and such. Does not seem to alter the shape of the piece, and once wiped off, leaves a nice, rich black color. I would check it daily though, as I have not tried it on any rubber parts with markings. In addition, you can use it on all of your vinyl surfaces, and even your daily driver. Great stuff!