So I've been vaping CBD vape juice on and off for a few months using an OBS Engine MTL RTA. I recently left the RTA standing for about 2 weeks with the tank about half full. A couple of observations on CBD. Gunks up coils a lot faster than normal nicotine vaping liquid. I needed to rewick with almost every refill. CBD left in an RTA for an extended time will leave a nasty, sticky residue on the inside of the RTA. Very difficult to get this off even with Sunlight and a toothbrush. If anyone can offer any advice on how to clean this, I'd love to use this RTA for normal vaping.