Actually, I use the highest proof isopropyl alcohol I can find. The higher the proof, the easier it evaporates. My last job was in a building with around 20 ophthalmic research labs, and they had 200 proof alcohol available to them!

I use Q-tips also, but I would imagine off-brand ones would work fine--if they are the kind with wood or hard plastic sticks, just be careful not to let the hard stick touch the glass.

Q-tips usually leave lint behind so I usually need to blow or wipe the lint off with a microfiber cloth after the Q-tip.

I guess I should mention I'm a Nikon user, but I imagine the Zeiss coatings are just as durable.