I've been cleaning high end cameral lenses for the last thirty or so years and I don't think I've ever hurt one. They've always said the same thing your scope maker has said about cleaning. I've always used camera lens tissue and cleaner because it supposedly protects the coating. Water will not hurt the lens, but it will not clean the lens very well either. Water smears what is on the lens and doesn't pick it up. I beleive teh lens tissue is better than Kleenex because it contains no oils, and camera lens cleaner contains no alcohol. Wal-mart sells a little kit to clean glasses that has some pre-moistened tissues and a little spray bottle of cleaner and a lens cloth. The pre-moistened tissue contain alcohol and I don't know that I would want to use them on good optics. The cleaner is fine and should be safe as is the cloth. Wal-mart claims the whole kit to be safe for cameras, binoculars, etc. I don't have to clean my scopes very much because they are protected with lens covers, but when I do, I use a Leupold lens pen, which I think is a very good option. Wal-mart sells those as well and also sells a generic version which is just as good.