i would take the stat out and screw the housing backup
undo the top hose from the rad to head
undo the bottom hose bottom right of rad
put your hose pipe in the top hose and use some sort of rag to make sure you get all the water going down the hose into the head rather than all over engine
then put the hose in the expansion tank and put the top hose form rad to head back on so it flushes another route
then finally flush the radiator with both hoses off
let it flush for a good 10 minutes
this is how i use to do it
also heater matrix pipes, you could try putting the heater knob on hot and see if it it circulates, alternately unplug the two hose and shove ya hose pipe in there
heard myths about dish washer tablets etc, i find a good long flush is the best way imo