You will need to do several drain and fills through the drain plug to get all the old coolant out. The process usually goes like this..
-drain the radiator with the radiator cap off until the fluid stops
- then put the plug back in and fill it with distilled water until the overflow tank/radiator won't take anymore, giving a minute for the radiator to let it all flow down
- Put radiator cap back on, then run the engine with the heat on low until the thermostat opens and mixes the fresh water with old coolant (This step goes much faster if you remove the thermostat, since you only have to let the engine idle for a couple of minutes isntead of until the thermostat opens).
- Repeat step one until all the stuff you drain off is crystal clear, at least 3-4 times.
- add concentrate coolant to 50% of system capacity, (Honda 2.4 capacity = about 5.3-5.4 quarts, so you need about 2.65 quarts of concentrate coolant to get 50/50).
If you have access to a garden hose you can give it an extra flush by draining the radiator the first time and running the hose down the fill hole with the drain plug off until the water runs clear, making the subsequent drain and fills cleaner.
For the overflow bottle you can remove the whole assembly and rinse with water, then premix 50/50 mixture and add straight to the tank after finishing the job.
Also if you have good access to the lower radiator hose, the radiator drains really fast from this hose and is easily flushed with a garden hose from the top of the radiator to the lower hose since it lets debri flow more freely than the small drain plug.