I only own one Vaporfexion tank, the original Pro-V cartotank. Honestly, it's just an "OK" tank compared to other tanks I own, and was quite pricey by comparison too. The Pro-V was the first tank specifally made to look good on a Provari with the Provari teardrops milled into the SS caps. I rarely use the tank anymore, as I prefer the look of the IBTanked's more.
I know the VPX comes in a few types of tank, including one that uses a rebuildable atomizer. Did you get the carto-only version? The VPX Reactor Tank's feature of an easy open top cap should make juice refills easy and bottom air flow slit assures plenty of air for the carto. I hope you enjoy your tank.
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Vaporfexion Pro-V cartotank
Most people using cartotanks have at least a few other tanks to be able to keep separate flavors in each one. Changing flavors requires changing out cartomizers and rinsing the tank under the faucet with running water. Only one flavor per carto, as the filler material retains the original flavor. There really isn't a good method to clean the cartomizers themselves.
You should be able to use the same cartomizer for 5 - 6 tank refills. Once the draw on the carto becomes stiff its time to replace the carto with a new one.