Geez, and I was about to offer some freshly bloogered cartos in the trade thread! 
popeye, I'm not attaching the syringe to the carto. Picture a syringe without a needle, like this:
I'm just putting that tip on the rubber mouth piece and squirting. The holes aren't perfectly sized, but the cone shape of the mouth piece adapts and seals it relatively well. I'm doing this right in the boiling pot with the cartos sitting vertical on the battery end. The flush water exists the carto through the vent slots on the battery end. After marring my cartos by trying to hold them with tongs, now I'm just doing them while they are sitting on end, and I flush a given carto until I accidentally knock it over I figure the bloogiverse knows when it's clean and will use physics and gravity to let me know.
popeye, I'm not attaching the syringe to the carto. Picture a syringe without a needle, like this:

I'm just putting that tip on the rubber mouth piece and squirting. The holes aren't perfectly sized, but the cone shape of the mouth piece adapts and seals it relatively well. I'm doing this right in the boiling pot with the cartos sitting vertical on the battery end. The flush water exists the carto through the vent slots on the battery end. After marring my cartos by trying to hold them with tongs, now I'm just doing them while they are sitting on end, and I flush a given carto until I accidentally knock it over I figure the bloogiverse knows when it's clean and will use physics and gravity to let me know.