Sorry here again, yes i did get a rough ish finish but as its the rubber bits that create the seal and create the majority of the friction it has little to no effect, i used slightly heavier than wet and dry but wet and dry does the job. Oil up the seals afterwards bleed them with magura blood first then either leave it like that or re bleed with water. Edit: Forgot to mention that if you use this method you need to make sure theres no plastic bits in the lever or it will jam in between the rubber seals and the plastic and un-do all your work.