I have two of them that I have used at various times over the years, the brushes are great as they are retractable, keeping them out of harms way, on the other hand, the cup shaped end that they advertise you can clean stubborn dirt off of the surface of the lens, can and does become a landmine, it is a imitation piece of chamois, that will allow dirt particles to become embedded in it and can cause scratches in the coating of the lens, if shooting in a sandy area, it could capture sand particles and cause a scratch in the actual element of the lens. As far as your mirror,the only thing I do on mine is use a blow brush, I never touch the surface of the mirror and I never use canned air, I saw the mirror in an F5 ruined resulting in a $400 repair bill to replace it..
Dave