flushing a heater core

Newbie question: What is the best way to bypass the heatercore?

Initially, when I pulled the heatercore, I blocked both the hoses. This resulted in too much pressure building up and the radiator hose blowing. So, after I found a blockage in the system and cleaned it out, I took the intlet hose off and took the return hose, coming from the water pump, looped it around and hooked it into the manifold. This seems to work, but there is still a light antifreeze leak coming off of the connection at the manifold. I figure this might be because the return hose is slightly larger than the sending hose. I know this isn't the greatest fix in the world, but will this do any damage to my car? Any suggestions?