I decided to flush my heater core today and I thought that I should share with you folks what I did.
Basically I took some old washer hose and cut the ends off and put them inside the heater core hoses and clamped them down good and tight...... Then let the water flow in both directions till clear.
On a side note: Make sure the hose that is the drain at the moment is NOT submerged in the water from the heater core. It creates a "cross connection" that whenever water is used elsewhere in the house it creates a small vacuum that will suck that crap into your houses water lines...... contaminating the water supply in your house.

 

I bet the heat will work a lot better now. The heater hoses themselves look kind of old & crusty, might want to replace those while your there so you don't get stranded.

 

That's next on my list lol along with the upper and lower radiator hoses... Going to overhaul the coolant system as a whole soon too.