i went through hell and back with my xj's cooling problems. this is the way i flushed mine, which didnt help because i needed a new radiator no matter what and ended up changing it in auto zone parking lot...
i pulled the plug from the drain dock- it's on the passenger side of the radiator a few inches up from the bottom. it kinda screws out, and i wouldnt even try it without some grips, trust me, it'll make it 10x easier. when you put it back in, it's a pain to try to put it back in by hand OR pliers, so i just tapped it in with a hammer, and that worked very well.
about flushing - i parked the jeep by the woods, took my garden hose and stuck it in the radiator cap and let it run full blast while i took a trip in the ford exploder to advance auto parts, got some radiator flush (i recommend getting a new 'failsafe' thermostat and gasket) and came back home. put the plug back in, added the flush, used it as directed, removed the plug, put the hose back in the cap and let it run while i went in and ate dinner, came back out, let it all drain, put the plug back in and added a 50/50 coolant and mineral water. mineral water is supposed to keep deposits from collecting in the radiator.
when youre adding water, let the jeep keep running and get up to operating temp. with the heat on defrost. it'll push out the air bubbles so you dont get vapor lock. i do this until i'm 100% sure theres no air in the cooling system.
i tried my best to help because i didnt know any of this when i had my problems. good luck!