Are you cleaning up a heavier polishing stage? If so don't completely throw White out of the equation due to how mild both the PC itself and Ultrafina are.
Why do they recommend a softer pad with this? I would assume you would grab white/gray for this product. But "blue"; I use that to apply sealants. I would think it would want something stronger to break down the polishes since it's on a PC doing the job.