Hi ya,
I have been doing this today.
Used garden hose to flush system thur, then used rad flush(ran engine for about 20 mins @ 2k RPM) to clean all the rust and cr*p out, then ran the hose thur again.
Have repeated the process again but have left the rad flush in the system over nite and will then flush thur with hose again.
Hope this helps.
cheeRS Barney