I agree with everyone here! Its MUCH more important to burp that system than anything else with the cooling system! Believe me when I say if you don't get all the air purged out of it, you are looking for trouble with a blown head gasket!
Easy way to tel if you got it all out, around 2-3000rpm while driving, flip your heater to hot. If you hear gurgling, you did not get all the air out!
I'd do this for a week straight! Every morning when you take off for work/school/whatever, as soon as you see the temp gauge level off, flip the heater core to full heat and listen for that gurgle. If you hear it, you'll need to park on a very steep hill, open that radiator cap (don't do this when its hot please!), then let it run that air pocket through the system and out the filler neck!
If you're really worried about the mixture being perfect, get yourself this:
http://www.amazon.com/Cool-Trak-3115.../dp/B000MIUJMO
or:
http://www.amazon.com/Prestone-AF-14...bxgy_263_img_z
Personally, I just dump a half gallon of distilled water in, a half gallon of toyota red (non premixed stuff), then put a little more of each in until its filled to the top. Close enough and never a worry of it ever freezing in winter. It doesn't take much to keep the system from rusting, you could probably get away with a 75/25 mix without problems, unless you live in Alaska or something!