Hotest water you can stand. Blast copious amount over lenses, both sides. This removes some grease and large grit. Put several drops of detergent on finger tip and rub onto thumb tip. Using thumb and finger coat detergent onto both sides of both lenses then rub gently. A few seconds is all you need. This removes all remaining oils and suspends any remaining grit preventing friction scratches during cleaning. Rinse lenses with hot water and gently dry with paper towel. Hold up to light to check progress. Remaining smears if any come off with paper towel. Been doing it for decades. It never scratches and it cleans like new.