Thanks and glad to hear that you are having success refilling your Canon.
Here is a video showing the "top fill" or sometimes called American Method :
The fill port being used is the original Canon fill port. The Canon plug must be removed and then replaced with a 5/32" dia. silicone plug. The Canon plug gets destroyed in the removal process but the replacement plug can be used over and over. These plugs are available from Precision Colors with their refill kits.
The alternative location is centered on the "divot" which is to right in the video and near the cartridge clip. An 1/8" dia. hole is drilled here with a brad point bit and sealed with a silicone plug (for this dia.) available from Hobbicolors with their refill kits.
Sometime during the life of the cartridge it is necessary to flush the cartridge. Having one of these ports open makes it a bit easier, IMO. The method usually involves adapting a 60cc syringe to the outlet port and gently forcing distilled water out through the open fill port. Some use tap water and adapt down from the faucet to the cartridge outlet port using tubing and fittings.
Flushing with the German method, the spoils are flushed out through the vent, which isn't as efficient. Not to worry though, as flushing is not needed very often. The tank to watch is the large black pigment ink tank....pigment-based inks are more prone to clogging than the dye-based inks.
It is good practice to call up a nozzle check once every week or so to exercise all the nozzles with a minimum of ink usage. If you are doing lots of photos and no pure text, your black pigment nozzles are not being exercised and vice-versa.
Don't do a cleaning, just a nozzle check printout to exercise all nozzles. Only do a cleaning if necessary...this uses more ink, esp. deep cleaning.