Well...first off, you need a dumped nand. You can use bootmii to create one and extract it with showmiiwads (I think). In any case, you should get a bunch of folders (import, meta, shared1, shared2, temp, title, ticket, sys). Move these over to the root of your USB device. Then use showmiiwads to install the wads to that emulated nand (change the nand backup path to the root of that USB device).
As for triiforce...I actually recommend using
triiforce_mrc. It's supposed to be just a graphical front-end, but especially with rev21, I find it to be more stable (could be just my setup). If you insist on using triiforce itself,
here's a link (the forwarder also contains a compiled version).
Perhaps the new cIOS will stir up some updates for triiforce*, but thus far it only uses the cIOS in slot 249. As for which version to use...I'm still testing out some base IOS'es for rev21, but to play it safe, I'd stick with rev17.
Still...I have to agree with niishou. The games that work work...but if you want full compatibillity, sneek is the way to go. And uloader may just have slightly better compatibility (and is IMO easier to setup).
*I doubt Marc Max will continue working on triiforce mrc...last I heard, he's busy with mighty channels.