Parking Clarification (Parks In & Out)

This July will be my first Off-Property stay in Orlando and we are planning on visiting "The Competition" as well as a visit to "The World."

In the latest UnOfficial Guide it mentions parking and Park Hopping. I need a clarification please:

If I visit and pay for parking at one WDW Theme Park, I can get access to parking at another WDW Theme Park WITHOUT paying by showing the attendant the receipt from earlier in the day from the previous Park? Is that correct?

And is Bus transportation limited to WDW Guests only? I remember riding the bus and sometimes showing Key to the World cards and sometimes not.

Thanks gang!

Your parking pass and receipt are good for the day at any of the park's parking lots. No problem driving from park to park. We also used WDW transportation with no issues as off-site guests. We normally drive everywhere, but if we wanted to take a bus to go eat at a hotel, it was no problem.

Thanks for the confirmation! Looking forward to a busy (and hot) July trip.