I'm polishing my combat boots before I go to raleigh. I'm using kiwi mid tan polish then buffering it after. On the rubber areas of the boot, the polish doesn't work great and marks are appearing where the polish doesn't take effect. Also there are black marks on the leather areas that keep appearing. At PRNC we were not told much on how to polish them, just to do it twice a weak and wear them in. Am I doing something wrong?