This is a video guide that shows you how to modify your Canon inkjet cartridge so it can be used for the Top-fill refilling method.
The video covers not only the process for removing the original fill ball, but also the various options available for plugging the hole after refilling including the limitations for Canon Multifunctional printers (eg: the MP, MX and MG models) and what you can use if you mess up (Aluminium tape saves the day!)
We also have a later video we created that deals specifically with the newer PGI-550/CLI-551 type cartridges below: