i do not fill from where the ball is, i use the german method, possibly closing the vent might help but then again it might force ink out of the exit port prematurely, but i will try that the next time
This is how my refill looks like for a cartridge that has been purged/flushed cleaned . The refill process is taken at different stages.
I never had to purge/flush a canon cartridge 8 years ago when I first started refill. I only started purge/flush canon cartridge ~10 months ago when I started to be experimental as I try to test out inks from different sources. As I do not want my result to be interfer by different inks so I purge/flush the cartridges. Otherwise under normal circumstance, I never had a need to purge/flush cartridges.