well if you can still get radflush i would use it, also i tend too take the rad/and/or pipes off and backflush it , I:E take a hose and squirt water in from the bottom end it moves some of the crap that will not get moved other wise, anti freeze buying premix you are paying for water which is freely available from a tap. or here at the moment stick a bucket out side the door for 3 mins, also if you mix it you know it is correct, no more than 50/50 though, neat antifreeze actually freezes at a higher temp thatn 50/50 mix
Merv