Does 72 hour visa apply if using 2 different airlines?

Hello,
We will be traveling from Thailand to Beijing with a 35 hour layover in Beijing before we depart for Los Angeles.
3 questions:
Are we eligible for the 72 hour free transit if we are using a different airline for each leg, meaning 2 different airlines?
Does the visa cost anything?
Is it a lengthy process at the airport to get it, or just a different immigration line?
Thank you!