Toothbrush , then I use automobile interior polish like ArmourAll Protectant plastic polish to restore the rubber. Make sure not to use too much or it becomes oily.

https://www.youtube.com/watch?v=aJaoS4IVE7A

this video show how to clean the white stuff

Or you can purchase and replace the rubber

You actually can replace the zoom ring, focusing ring rubber they do not put adhesive between the rubber surface and lens barrel.

for your case I think ur lens is 28-70 Tokina/Nikon? you may contact tokina ask them for replacement.

or you can find it in ebay:
https://www.ebay.ca/sch/i.html?_odkw=tokina...g&_sacat=182074

I try search awhile ebay seem like no people is selling this LOL. try contact Sony service center?

brush does not work?

You can actually remove the rubber, and clean it thoroughly under running water. I actually did that to my olympus 150mm f2.0 lens. But the rubber will become elongated but still useable. I not sure about sony, but if the rubber are not glued to the lens, you can actually try it.

Another way is your can try this video tutorial:  https://www.youtube.com/watch?v=MJCyUkc8KEk

Just use alcohol swab. It will do the job.

Just go to nearest pharmacy and ask them for alcohol swabs.