You definitely did not eff up getting the KGO. They are a very good battery style.
I prefer the "clear" EMDCC's because you can see exactly how much... and where.. all the e-juice is. FYI, I really..really.. LOVE these things and so, here is what I do to fill them up in a way that makes me very happy:
Use fairly thin juice. I like 80PG/20VG. Max VG of 30%.
I drip the liquid in from the top and soak the filler about 1/2 way then I take one of my husband's socks and do a VERY GENTLE "taryn spin" with the connector end facing the end of the sock... so that the liquid spins down to the bottom but also leaves some sort of empty-ish spaces. Don't try to soak the filler... this is never a good idea... if you do that, spin the juice out the other end until it's about 2/3 soaked or less, only. Stop worrying about how many ml's your'e dripping into it... and just look at it.. that's why I love the clear plastic ones!
Blow through the top end to make sure you haven't clogged up the air-hole. If you can, best to let the whole thing sit for a day and wick better... much improved plumes of vapor plus flavor. From then on, just top off the EMDCC when needed to keep it kinda moist. I have yet to actually burn one. They rinse out very easily under tap water in the sink, no need to boil or use alcohol or any of that fuss. Even the dark liquids usually rinse right out. I use them 3-4 x each and then toss them. Way cheaper than any other cartos I've experimented with.
If you get the "baby bottle" type rubber tips and don't like them, cut them in 1/2 with some sharp scissors and insert a regular 510 drip-tip. They work and look great
Only 2 issues I've encountered are: condensation (need to use a tissue or swab to wipe it out occasionally), and the clear plastic casing will crack if I use any niquid containing cinnamon