fingerpicks

Standard finger-pick technique is to pick down-only with the thumb and up-only with the index, middle, and/or ring fingers, depending on your style. Some have developed the ability to pick UP wih a thumpick (maybe by grasping with the index finger?) as if it were a flatpick, but that seems a bit extreme to me. It's darn near impossible to get a figerpick on the index etc. fingers to strum down without getting hooked on the string.

My personal preference (maybe not actually GOOD at it!) is to use a flatpick along with the nails of my middle and ring fingers. That's a "country Telecaster" techinque. Also catch a video of Roger McGuinn (The Byrds) doing that on his Rickenbacker 12-string. You hear that extensively on Mr. Tamborine Man, Turn-Turn-Turn, Bells of Rhymney, etc.

For extra volume when playing acoustically, I have a set of ProPiks that are mostly open across the middle, allowing the fingertips to feel the strings; the picking area is really just a thin arch that runs along the edges of the nails.
http://www.guptillmusic.com/propik/fingertone.html

Alaska Piks are sort of similar and might work both up and down, but I find them uncomfortable. Your mileage may vary.
http://www.alaskapik.com/

Then again, maybe this is what you're REALLY looking for:
http://www.bluegrasswest.com/ideas/sti-105.htm

Hope this helps!

- Ed