I use cotton q-tips, isopropyl alcohol and gently wipe in a circular pattern... Is that too harsh?
What's harsh is the dirt, not necessarily the Q-Tip itself. Say there's a tiny piece of sand stuck in some grease residue on your lens. If it gets lodged on the tip of your Q-Tip, you could end up with a circular scratch in the glass. Considering the shape of a Q-Tip, you are exerting tremendous force using one compared to a balled up tissue. Tissues are much safer than Q-Tips. Also alcohol will only dissolve certain types of dirt. It is very good with grease residue as a final cleaning effort. But has almost no effect on water based stains.
I have worked repairing cameras and binoculars for over 30 years. Not to be gross, but it's natural for people to spit as they talk. It's normal to see optics covered with tiny spots that are actually dried spit. To say nothing of what happens when you sneeze. You could clean all day with alcohol and have no effect on this type of spot.
My cleaning procedure at work is to first blow off loose dirt. A duster from a computer or camera store is excellent for this. Then some type of lens cleaner on an ordinary tissue rolled up in a ball. Ordinary Windex is fine for this. Don't use so much lens cleaner that it gets on the edge of the glass and bleeds in between the metal mount and the glass. More of an issue with camera lenses than flashlights that usually have rubber O-rings at the edge. O-rings tend to cause their own problems as far as grease they are covered with to prevent drying will bleed onto the glass during cleaning. The first cleaning should be done with as little pressure as possible. Once you get off the initial dirt that might contain abrasive particles, in a second cleaning with lens cleaner you can scrub stubborn spots if necessary. A final cleaning with alcohol will remove the residual grease from the lens cleaner. The trick here is to follow the alcohol cleaning with a dry wipe to get the residue before it dries on the glass. We have a reagent grade of isopropyl at work that's 99.999% pure. It's almost impossible to get glass spotless with it. It dries so fast it always leaves a grease trail where it dried. I always ask myself if it's so pure, what is the residue it leaves behind. I dilute it with ≈25% distilled water. At home I use Walmart rubbing alcohol for cleaning. I use the one that's 70% isopropyl alcohol and the rest is 30% is distilled water. Obviously if you have the type of rubbing alcohol that contains lanolin to replace skin oils, it will be useless for lens cleaning. The water slows the drying just enough to be able to use the dry end of the same tissue to wipe up the residue before it dries on the glass. If the tissue is folded over in several layers, it will help prevent grease from your fingers bleeding through the tissue. Washing your hands first will help.
Windex and Walmart rubbing alcohol on the same tissue you might blow your nose in... Yeah I know it sounds like I'm joking. Believe me when I say cleaning glass is 90% technique and 10% materials. There really is an entire science devoted to this subject. We have special disposable Micro-Wipes at work we use for their low lint content. At home I get just as good results using ordinary Puffs. The ones without the grease in them. In my experience, when a camera store sells a lens cleaner and says, "This is the only thing you need", well not so much. No one single product can do the whole job as well or as easily as several products used together.
Also my technique is strictly for cleaning glass. Anything you use to rub on plastic is going to leave micro-scratches or sleeks. The same holds true for aluminized plastic or coated metal reflectors. Reflectors being on the inside of the light won't need cleaning that often. Just blow off the loose stuff with a duster and call it a day.
