I'm trying to figure out a way to do "bullet holes" but actually apply the texture at the shader level? If I'm dealing with a model which doesn't have a "flat" face I'd like to be able to wrap the "decal" across the model. Anyone point me at a tutorial that will do something similar to this.
"Flat" face is not a requirement for the decals at all. Here is a visual explanation of how you can project a decal geometrically onto a complicated object.
Also there is that one site which gets referenced quite often here, it has a DX 10 implementation of such decals, search for "volume decals".
Check out paged/virtualized texturing system such as MegaTexture. These could be used to replace decals by drawing into the texture pages as they get paged in.
What I had been imagining is determining during the "picking" determine the specific position on the model and pass that exact position to the sharer along with a bullet texture to apply. Of course this still results in the issue of "filing across faces. The geometric projection seems the best option.