Usually when I play in a studio and have had hum problems, you have probably noticed that if you turn to a certain angle from your amplifier that the hum will usually decrease. You are actually picking up stray magnetic fields or EMF signals. What I have done and had worked on occasion is instead of moving my guitar all around to reduce the hum, I just simply moved the amplifier to a different angle. I'd put the amplifier on it's side, backwards and even upside down. This seemed to help the field angle and made the engineer much happier.
You can shield your guitar all you want but it doesn't reduce the stray magnetic fields that can penetrate your high impedance single coil pickups. You will find hum to be much worse with larger powered amplifiers with large power and output transformers. Also if you are recording with your computer controlled studio, remember that old-fashioned CRT computer monitors will radiate signals that will cause noise in your instrument.