I use both methods to refill carto's. I find that if using the condom method, I can cap the top and then store them in my
Bottle Buddie Keychain from sweet-vapes (thanks Dayna!!) If you do it right,(condom method) and go s-l-o-o-o-w-l-y, the carto will suck the e-juice into itself(at least I think that's what happens LOL).