If its only a "bit" of dust on the mirror and its not affecting the views leave it alone!! Only clean a mirror when its necessary as no matter how careful you are you always do some damage to the finish and the fewer cleans you can do the less damage to your mirror.
i am on rob on this one. if you try to clean it theres a better chance of damage then if you dont. but each to thier own anyhow.
a little bit of dust does absolutely no harm to viewing
I can only agree to what people say here: little bit of dust doesn't do any harm and doesn't affect your observing in the slightest. The most horrible thing you can do is overclean your optics, it might damage them more than provide any benefit.
I also wouldn't recommend to shine any light directly at your mirror, you're always gonna find something. As long as it looks good down there in the telescope, it will work well.
