That Opti-Clean stuff sounds like a nightmare. Read a forum thread a while back where someone had the same gummy disaster with a different new "miracle" cleaner on a Minolta. For these old metal shutters, it seems like sticking with the classics is the only safe bet. Heard a lot of good things about plain old Ronsonol lighter fluid, the kind in the yellow bottle, for this exact job. It's basically just clean naphtha. After a scare like that, going back to the simple stuff feels like the only smart move.