Replying to Cleaning the inside of lenses

So, I have crowbars and i know pretty much how to maintain them and cleaning, but one thing i am not sure of is the inside of the lens. i know not to wipe it when it is wet because it takes away the anti fog properties, and to wipe it lightly when it is dry. But the problem is that then lens is very dirty on the inside and im not sure how to go about properly cleaning it without damaging the lens. Any help? Anyone know of any methods?

thanks