The 808 threaded cartos that we used when we were using cigalikes were definitely very easy to refill with eliquids that we liked, at the nicotine and pg/vg levels that we found worked for us.
You might want to check with Revolution Vapor for blank, refillable cartos. Their customer service is excellent - I had a few questions when we were still using cigalikes, and they always answered promptly. You can use their "Contact Us" form to make sure that their cartos will work with your Greensmoke batteries. They also have prefilled cartos.
Personally, my daughter and I are happy that we moved on from cigalikes to Kanger Evod setups. The cigalikes worked very well to keep us from going back to smoking (we quit smoking around 9 years ago, cold turkey, and started vaping around 3 years ago when stress and cravings started making smoking seem more and more desirable). The major problem we had with cigalikes is that when the carto is dead, "it is dead, Jim". With the Evods, we get more vape time to the charge with the batteries, and the coils can be cleaned, rewicked, and recoild, depending on your choice of how involved you want to get with it.