When enhancing with a smith, try to use a +30 hammer (+60 if you can afford it). This will stack on top of your 120 smith and you have a 150 or 180 smith. It makes a big difference in success. I've also read somewhere that it doesn't matter, but I use a luck suit and a high boost talisman as well. I DO succeed far more than I fail, I just happen to fail on the good pieces more frequently it seems, but that is consistent with what EA says should happen. FWIW.