I've been using both the "condom" method, which I find to be too messy and I also drip the juice in from the top, averaging about 25 drops. I've been using Halo and Smokeless Image juices. I usually vape them until I taste the burnt taste, due to the fact I'm away from home most of the time.
I think you may be underfilling your cartos a bit and vaping them dry. I usually get at least 33 drops into my cartos, and top them up with a couple of drops every hour or so. Cartos should always stay wet, and when they don't you kinda 'fry them' and burn the filling. Once they're fried, they may produce vapor but they don't hold as much juice and they don't produce any flavour.
I use the condom method and fill the condom almost all the way to the top, and slowly insert the carto a bit, let it soak up, push it down more, and so on and so on. It gives the carto a chance to really soak up the juice. Here's a good vid about how to fill cartos. He's filling a 510 carto, but the process is the same for 808 (Volt) cartos.
You might want to either bring a small bottle of juice with you (some vendors sell little keychain bottles) or fill up more cartos to use when you're away from home so that you don't vape them dry. You may want to pick up some new blanks, in case the ones you're using are burnt.
Hope everything works out for you okay!
