There are dozens of opinions on the best refilling method. Learning not to
overfill will save you mess, auto batts, and wasted juice. The centrifuge spin
is really unnecessary in my opinion.
If you put the buttplug in the batt end and fill from the mouth end you can't
fill up the center hole. Then all you have to do is stop dripping before the
filler is overfull, which you can see.
Don't ever fill a cart while it's attached to an auto battery.
I'm about to wash a large batch of used carts, like about 40 or so. that have accumulated. I plan to experiment a bit using hot water and ETOH (alcohol)
in different sequences. Also squirting the alcohol directly onto the atty coil
using a syringe to clean it. I'll also sort them by whether they show any
brown discoloration around the center tube - evidence of burning.
3-pc users are busy filling forum threads about modding their carts, with teabags, fishtank foam, metal screens, and probably at least 1 new idea since I last checked. OTOH, we carto vapers discuss, cleaning and refilling techniques which
make vaping truly economical. Where I live (NYC) analogs are over $10 most places,
maybe $12 or more in hotels and airports, so saving money by vaping isn't too difficult.