I removed the coolant temp senor to replace it and noticed allot of loose rust built up around the rear cylinder. It was built up to the height of the temp senor, this engine has never been rebuilt. So fare I was able to remove about a half pint of the loose rust with my magnet and am about to pull the drain plug on the opposite side of the block to get as much out that side with my magnet as well. I will also be washing out the block with water to remove as much of this loose rust as possible. I'm installing a rebuild radiator as well and really don't want this loose rust to get into the radiator. I've seen these engine block flushes but am learly of using them. Has anyone used these flushes before? If so what kind etc. 

  I was also thinking of starting the motor and leaving the top radiator hose disconnected and keep a steady flow of water running into the radiator fill cap to help flush out the rust. Again any ideas or past experinces would help. 

Thanks
Eric