Once you get it in to an icosidodecahedron you then extend the pentagonal faces (usually with Milliput or some other sculpting material). In brief explanation, stick credit-card thickness pieces of plastic through the cut lines, then build up a chunk of sclupting material over the penmtagonal face. This step doesn't have to be perfect, you just need to san and fill (alot) later. I might be wrong though because I've never really made much mods before
