I have 3-4 pack of Blu cartmizers that I've been successfully refilling. However they've all been refilled around 4-5 times now and I think the coils are started to gunk. Have been cleaning in warm water, 91% ISO and then 2-3 days of warm air drying. No way to do at dry burn though so I may be at end of life. Also trying a Kanger mini ProTank 2 which is just excellent. Long, easy hits and NO dry/burned wicks (to date). Bottom coils seem most appropriate to me. And NO leaks (unlike my CE4...).