Share 'Here's a VERY noob question...'

The only kind of bike racing I've ever done was BMX... so I'm relatively clueless on this issue. I bought my first pair of true biker shorts a few weeks ago after my first CX race. After a few remounts at speed, I totally understand why you need them. So my question is, what are you supposed to wear under them? Plain old cotton undies? Vasoline and freeball? My running shorts have those innerl…