how does one create a 2nd wallet for spending?
If you move wallet.dat out of it's folder a new empty wallet is created automatically.
but then u can't send btc to that 2nd wallet from the 1st wallet on the same computer.
You can, by very careful file renaming while the Bitcoin client is closed. I wouldn't make a habit of it though, doing it only as necessary. Some people say they've made custom tools to help with easy wallet-switching, but I don't know if any of them have been released publicly.