I have some conventional green concentrate. Maybe I should add some of that and them fill it up with the yellow 50/50?

 

that water is left in there is fine, you do not want 100% antifreeze anyway. The 50/50 mix has water already mixed in. And you have to add water to full strength antifreeze anyway.
I would not mix. conventional with your new stuff.

 

How much should it take with water still in there? I hope at least 2 gallons.

 

according to Rave, 12 litres or 3.17 gallons to refill and 1 liter is normally left in there. and bone dry would be 13 liters or 3.43 gallons.

 

It only took a gallon and change. I'm assuming that is because there is still are in the system? Should I run it to get the air out (on the ramp/slope)?

 

my driveway has a slight slope on it and I just open the bleed valve and fill the reservoir up to the top and about that time, the bleed valve starts overflowing and then tighten up the bleed valve.
Not while it is running or hot.

 

While filling the tank, make sure you squeeze/pump the hose while adding coolant. The bubbles will rise at same time adding the liquid.

 

I will try to squeeze the hose because I do not have a bleeder valve. I had to take it out a few months back because it was leaking.

 

Discovery usually bleed itself through massive leaks. Dont worry! LOL! Cheers!

 

I guess I didn't explain my instructions well enough.

Yes, when you drain the system there will still be fluid left in it. That's why you need to do it more than once, until what comes out of the system is clear. That means what is left in the system is "mostly" just water. You then fill the system with antifreeze CONCENTRATE, not 50/50, to get to a near 50/50 mix in your system. If you refill with 50/50 you will end up with something like 25/75, which may be adequate to prevent freezing depending on where you live but which is not the objective.