Not sure I understand your question diss - completely get rid of what? The faces? The leaves?
Skip covered brushes won't do anything - the point of skip is that faces textured with it are ignored by the compile tools (which isn't entirely true, but its near enough). If you have a brush covered entirely in the skip texture, then there is no purpose to the brush (unless you created it to aid you in hammer, but that's another story), so you might as well just delete it.
Nodraw exists precisely for scenarios like the ones being talked about here - creating solid brushes for BSP/VIS purposes, without adding any rendering costs. If you want to simplify your BSP, then you can use nodraw brushes to make a simpler, not necessarily visible "hull" to your level, and use func_detail brushes to fill in the awkwardly shaped architecture.