Reading Multiple switch inputs
You could use a MCP23017 or similar.  Its an IC that provides 16 IO ports via I2C, I think you can have 4 of them so that should be enough for both hands.

Or you could use resistors.  All the buttons are connected to a single analogue port.  The resistors are chosen so that when you press any combination of buttons you will get a unique reading at the port. So if you press button one and get a reading of 100, press 2 and get 150, press 3 and get 200, etc.  So buttons 1+2 give you 250, 2+3 gives you 350 and 1+2+3 gives you 450.  The problem with this is the maths get out of hand very quickly and the IC is &lt; $1.