raidiator drain plug

I have a 1994 Ranger with 4.0 manual 5 speed with AC. the truck has been operating at a warmer temp lately so I decided to flush the system.

I follwed the Haynes manual guide lines and I have a question... when I open the drain plug on the bottom of the radiator (cap is off and system is cold) should all the fluid drain from the system? I am getting nothing more then a trickle. I Left the cap off and started the engine...no increase in fluid from the drain plug. I have installed a flush valve on the return hose from the heater and I opened it up with the truck running to see if I had a flow and I was getting a good flow up to that point. I have flow into the upper hose and into the radiator... just seems to be something plugged in the drain plug. I pulled it completely out and no increase in drainage from that plug. I tried puitting the radiator cap back on and turning the hose on into the flush valve. All that happend was the over flow resivior filled up and over flowed.
Any suggestions? Should I use a flush cleaning detergent?

any help is appreciated

drain plug is just what it is, a drain plug. you shouldnt worry about flow here!!!

but if I open it shouldn't it drain? My truck was hit tonight and is possibly totalled, I will find out soon, so I may not need to worry about it... I am sooooo pissssed