WD in WD-40 stands for water displacement and so is not really a lubricant and once it dries, it leaves a gummy film. Also, if any of the petroleum distillates gets onto the rubber ball, it will evenutally swell up and be ruined. So do not use any oil or solvent.
If you must use a lubricant, use a spray silicone lubricant. They won't damage rubber and when the carrier dries, it leaves a dry, non-sticky film. The problem is if you get any silicone on any friction surface, like the ball itself or on the rollers, it will tend to slip and defeat the friction characteristics needed for proper operation of the mouse.