A few years ago, I decided that total immersion was the way for me to learn fingerpicking. I put my picks away, and for two years I used only my fingers. My home guitar was a six-string, and the 12 was at work. I practiced on each, every day. Anything I was learning on a six-string, I also played on a 12.
Even though I have what some consider to be a pretty loud 12-string (Guild JF30-12), I really had to yank the strings to get sound out of it without a pick. So with the flesh of your fingertips, or even with fingernails, the projection was minimal. But I played everything. Single string (single course, as above) leads, bass-note turnarounds, even bends. So I recommend trying your whole repertoire out on your 12 to find out what works and what doesn't.
I eventually joined a church group. My 6-string had intonation problems, so I played my 12 in church every week, and continued to fingerpick. Even miked, I had trouble getting the sound out. (The exaggerated yanking and pulling on the strings gave an interesting and I would say intense backing for some solo gospel/bluesy songs in our repertoire.)
I switched to a pick, eventually, and get the full clangy sound you want a 12-string to have. Now and then, I try finger picks, but have not yet mastered them.
A few points that haven't been brought up yet:
1. It takes a lot more left-hand power to fret a 12. Especially in the beginning, you'll use barre chords less.
2. The 12 is not as "fast" as a six-string, so single-note transitions and grace notes that just happen on a six will take some practice to get right on a 12.
3. I have heard that Leadbelly tuned his guitar way down, (to C, maybe), which really changes the sound, especially the bass notes, making them, to my ears, almost piano-like.
4. Current acoustic players: take a listen to Paul Geremia
JK
