Cheap way to clean lenses and metalparts is isopropylen alcohol.
The blue one you can buy at pharmacies and buildersshops.
Use 50/50 with water and you have the same solution as any service
technician.
Another trick is that behind the laser itself it is a copper feather
that you can bend a little bit because they get softer by wear and
tear.
All at your own risk of course.
But this is what i do.
