Get a truckload of distilled water and follow these directions:-
http://www.obsessiontelescopes.com/l...ror/index.html
Seems to me that one has to be careful but not over precious. Get as much loose stuff off first with blower bulb and clean water. Then soak in warm clean water with minimal detergent. Clean cotton balls drawn across surface in straight lines under their own weight. A new ball for each line. Wash off. Rinse with distilled. Stand on edge with towel. Use tissues rolled to points to lift off remaining droplets.
Yes, might be a few streaks and spots remaining. Don't worry about them.
Major risk is the potential damage due to banging, dropping, falling over, scratching with rings etc., not the washing process itself.