From the sounds of how cruddy it is you should just skip the draining stuff and go get the system flushed. It needs it, the coolant should be bright green in Fords. But if you insist on just draining it try the plug thing, tho it will take a while to drain. Or just pull off the bottom radiator hose. Either way take of the rad cap to let air into the system, and when you fill up again you will have to go thru a few heat cycles and top off the coolant a few times once all the air bubbles get out of the system.
2001½ F150 5.4 XLT Crew Cab- 3.55 gears and towing package, true dual glasspacks with x-pipe, AEM intake, SCT X3 with VMP custom tunes, E-fans conversion, full stereo system, HID 55w heads & 35w fogs, 35% tint front & 20% rear, Lightning head lights & tail lights, all interior & exterior bulbs LED