Easy Way To Flush Out A Converter?

The engine was shot and the car only had 40k miles on it so it looks like it'll be just a normal rebuild, I don't expect to find metal or anything but I did want to get as much of the old fluid out as I could. I surely don't want to go to the expense of having it cut open, shipping both ways plus the cost would probably put it in the area of buying a rebuilt one.