Well,
What i did was run the lamp under warm edging on hot water for a few minutes. Then prepare a few cotton tips (i think Americans might call them Q tips ? I'm not sure...like a thin hollow plastic tube with cotton on both ends), and also a small plate of liqud dishwasher/soap (don't mix it with water, leave it as thick as possible). Leave water running, get one cotton tip, saturate it with the liquid, then remove reflector from running water and GENTLY wipe the reflector. If it's too thick, place the cotton tip under the running water for a moment or two, then keep wiping GENTLY on the reflector. Once i was sure i wiped the whole reflector, ran in under the warm water for a minute or so, then use a new cotton tip and repeat the process 3 times or so till you're happy with it.
As to whether i damaged it ? Yes, i put some (very) slight surface scratches on it but that was my judgemental error. The surface scratches are on the bottom of the reflector and i remember wiping that area gently, but not as gently as with the rest of the reflector. The rest of the reflector looks pretty much like when i got it
.
I think the reflector doesn't get scratched because the thick liquid dishwasher soap (or whatever it's called =P) doesn't contain fibres (like water), so it acts as a buffer between the reflector coating and the fibres of the cotton tip.
Once you're done washing it, get a can of compressed air and use it liberally to blow the water off. Don't use a hair-dryer unless your hair-dryer can blow air at the ambient temp. Evaporated water leaves marks on the reflector. Also with the can of compressed air, try to keep the can upright...don't tilt it much or the propellant may come out as well meaning you'll have to clean the reflector all over again.
Goodluck and of course, YMMV.
Ps. Did i mention be VERY gently ? And probably wouldn't try this if your dishwashing liquid or whatnot isn't very viscous.