Most or the cameras I receive for repair have very dirty lenses and some have what the customer describes as "cleaning marks". There's no such thing as cleaning marks. call them what they are - scratches! They may be very light scratches only penetrating the coating, but they are scratches. How do you keep the lenses clean and avoid scratches?
Experience is the most important tool in cleaning lenses as it is in anything that requires skill.
Have you seen an optician clean a pair of glasses? He does it quickly and easily. And he gets them sparkling clean. And - no scratches. How does he do that? - Practice, practice, practice. He cleans several pair a day 250 days a year. That is the professional secret! Just practice.
So -- Don't practice on a fine, expensive optic like those found on Rolleis. Practice with some old piece of glass that you won't cry about when those "cleaning marks" appear. An old pair of glasses, a cheap pair of binoculars an old point and shoot camera, or any other worthless piece of glass. Keep practicing until you are consistently successful before cleaning your Rollei lens.
You will need some lens cleaner. Any water based lens cleaner is ok. For some stubborn dirt particles you can use some denatured alcohol. Get an air blower. I've found that one of the handiest portable air blowers is an ear syringe you can buy at the local drug store. You can also use an air compressor but be sure there is no oil or water in the air line. You'll need a soft brush. A sable brush is ideal. Also get some soft lens cleaning tissue and Q-tips. The lens tissue sold at camera stores is best for sensitive surfaces such as plastic viewfinder screens.
First blow off whatever particles you can with the air blower, then use the sable brush. Now all the looser particles are gone and usually this includes the largest ones, the ones that cause scratches.
Rule number one - Be gentle!- Don't scrub or rub or use force in any way to clean a fine optic!
Take a lens cleaning tissue and add some lens cleaner. Wipe the dirt off *gently* in a circular pattern starting from the center of the lens and working your way in a spiraling pattern to the edges. Then take a dry tissue and repeat *gently*. If there is any dirt left try to clean it with a Q-tip *gently*. If there is still some stubborn dirt try alcohol *gently*.