Oh boy. This sounds pretty tough. I use a thumbpick on occasion, and alternate with bare fingers if I'm playing something like West Coast Blues. The thumbpick I am currently using is a real heavy plastic one with the National Resophonic guitar logo on it. I gave up playing 12 string guitar quite a few years ago, and there are times when I wish I still had one. Twelve strings are great for ragtime, IMHO. I have a real heavy attack naturally.....hmmm Sorry Rick, I guess I'm not much help.
Jim