It is probably best not to try and clean an isolated section of the mirror until you can clean the entire mirror with detergent and then a rinse over the whole mirror with distilled water and left to dry as per recommendations posted here on IIS in the projects and articles section.
A small mark on the mirror will not effect overall performance and, as many have said before, optics should be cleaned only occasionally and when really necessary as mirrors are very fragile and should be handled with extreme care. Some people leave their dusty mirrors for months sometime years without cleaning and views are still good.
If your scope is fairly new you should not need to give your optics a clean for some time.
Cheers Rick
