I've managed to remove a front cone on a non-C RB 90mm using a tightly wrapped camera strap - but this won't work on my C 90mm. What other methods could I try? What about one of those Zyliss bottle openers?
Thanks, I was trying to undo the barrel - but now I've unscrewed the beauty ring instead and can remove the front group. I'm able to clean clean some of the dust out of it. Seems quite embedded so may need to use some alcohol and a lens tissue.