all these suggestions can help, but only if the water is flowing in the motor. at the least, you need to flush as much crap out of the motor as you can. the back flushing kits work sometimes...but, the only good way to do this is pull the motor, knock out all the freeze plugs and flush and scrape all the crap out. PIA i know, but worth it. p.s. heater core is going to be suspect after all this time too
