Thats the key to condom filling boges NOT RUSHING . I condom fill from the bottom also with the white cap off on the other end so i can see where the juice is at . I fill the condom with 35drops and slowly push it down .You will see at reach the top of the airtube about when you get half way down the condom .Then i go slow and keep the juice at the top of the airtube and it creeps down . By the time i got all 35 drops in the top area around the airtube is completely dry and no juice had flowed over the airtube .When i pull the condom off i put the last drop thats in there back onto the top and drip 4 more drops on the top .Then give it a thermometer shake and slight suck (Not blow ) into the top of the carto and your done with no a single drop of wasted juice or and mess to clean up or wipe off the carto .Airhole is also free of juice . When you suck not blow it doesnt leave the carto out the battery end where you need to wipe it up ,it just goes into the filler over the airtube .I dont even need a paper towel anymore
When i make holes for tanks i use two 1/16" drill holes .
All this Sucking & Blowing is getting confusing.
I'm not gonna admit to it. But, be careful sucking, you may get some juice on your tongue.