Yes you should be able to use V4L cartos, batteries (I recommend manuals so you can drag softer). You should also be able to use blank V4L & KR808D-1 cartos (standard resistance, not the LR ones). You may also be able to use the D1 and Greencig 300/400 cartos at leCig and the cartos at Bloogplanet, and ones at VapeSafe.
There are some slight differences in the notches of cartos and batteries that may make some KR8 threaded carotos not work with some batteries. Buy small amounts first to test.
Be sure to drag into your mouth first, then inhale. Drag slowly if the autos will let you.
Breathing vapor at first will seem foreign. And some flavors are very strong and a bit harsh. Also, cheap cartos may have 100% PG base
juice and the nicotine's skin irritation is hardly buffered by PG. When I refill with my own juices I use 70pg/30vg juices when possible.
I find soft-cap prefills I like OK and I usually use those and keep topping them off with a compatible juice I prefer. I like the WOW Vanilla cartos at V4L - a rich sweet marshmallowy vanilla, not too harsh. I like WOWbacco
- a very chocolate tobacco (and WOWboy is the same w/ a bit of mint).
I recommend you get a manual battery. The KR8 manuals still have a hole on the end but it's harder to damage or kill them with juice drips because they don't use a drag sensor there like autos do. You can put a DSE901 atomizer (standard resistance) and drip tip on a manual KR8 battery and use that to try juices (be sure to get rid of the primer on the atomizer first - primer tastes bad). Then you can buy little juice samples various places and find so good juices for refilling cartos. Note - no matter how careful you are refilling cartos, occasionally one will drip onto the end of the battery - yet another reason to get a manual battery. When adding juice to a carto always have it off the battery. When do clean up any drips, blow into the threaded end to clear the air channel, and sop up any loose juice above the stuffing. I use a plastic drip tip from LiteCigUSA.net as a mouthpiece on the carto - easy to remove when I need to add a bit of juice.
Some manual batteries here w/ cheap shipping
KR808D-1 Manual Battery