no petcock, no problem
Just loose the clamp on the lower hose and move it out of the way. Work a screwdriver under the hose till water drains out. You have about four gallons of coolant so have enough pans to catch it all. I have used a short plastic box that I bought at WalMart. The ones with a lid used for storage.
Or the pan you use to drain
oil into will work.
Dwight