Cooling System flush, how to refill PROPERLY after a flush Options

[ksporry]

Guys,
Am brand new here. Today I flushed the cooling system of my Celica GT. I was not aware of any drain plugs on the engine block, so I'm not sure if I flushed it correctly.
Basically what I did, was I set the heater to full on, hoping this would flush the cabin heating system as well. Then I disconnected the two main hoses between the engine and the radiator. With the radiator empty, I reconnected the bottom hose, and ran the engine until it started pumping water out of the upper main hose. After that, I filled it up with water (about 2.5-3 liters each time) and let the engine cycle this out again. I did this about 10 times until I saw clear water come out. Then I filled up the radiator with half the previous amount (so about 1.5 liters) and added one of those cleaner chemicals (as per instructions on the cleaner). I followed the instructions which said I had to either drive it 30 miles or run it high idle for about 10-15 minutes. I ran it about 20 minutes. Again I detached the top hose and let the engine spit out the stuff.
Filled up the radiator again full (still only about 2,5-3 liters, which seems very little to me), and let the engine spit out all the crap. Followed up with two more cycles like that, until the water was clean again.

Since tonight I read about drain plugs for cooling system, which I did not use, I wonder if my method was adequate.

Also, I wonder what the best next step is. I find it hard to believe that the system only takes about 3 liters of coolant. To me that sounds like the radiator taking 3 liters which is much more plausible. I now want to fill it up with coolant. Assuming that indeed the 3 liters fill up the radiator only, I am wondering if I should poor in the coolant up to filling the radiator and then leave it at that (unthinned coolant fluid. I'm considering that there may be another 2 or 3 liters of water in the system).
I also wonder what i should do to fill it up properly. Should I fill it up and then run the engine hot without the cap on the radiator? Should I wait and see if the level in the radiator drops, and then top it up again? If anyone could give me some instructions (before I blow my engine...), that would be great!
Also, what type of coolant should I use? I know of 2 types: cheap blue all purpose coolant fluid, and red coolant fluid (which I also know as VolksWagen coolant fluid). A friend of mine said his dad used the red stuff before in a classic car with a steel engine block and found it rusted the engine block from inside. He thinks my engine block may also be steel and therefore corrode if I use the red stuff. Any advice on that?