Wash your hands with hot water for a good 2 minutes to soften the skin. Scrub your fingertips with a scrubber to remove any dead skin.
Lay the lens over the sink (inside up) and fill with warm water and a good 2 tablespoons of dawn dish soap. Add the soap after the water so that it doesn't cause a lot of bubbles. Use your fingertips to lightly wash the inside of the lens and rinse with warm water. Use compressed air to blow all water out.
This is the method I use with every set that I do and it never causes scratches.
Threaded Mode
