Dancing Cat Records has a number of excellent slack key artists, and you can get a sampler, "Masters of the Slack Key Guitar" from them.
My personal favorite is Keola Beamer, but some of my friends feel he's not trad enough and prefer others like George Kwan and Ledward Kaapana.
I would suspect that the tunings aren't secret any more, since they are named and described in the liner notes to the CDs.
Some of my favorite music to massage by.
Mahalo nui loa,
Blessings,
Barbara