Hi Jvapes,
I've been using my subtank for well over a year now, I still get dry hits when I chain vape. One trick i'm doing is to draw hard on the tank without any power, you'll immediately see bubbles from the side juice holes come up. I've also experimented with the length of cotton when wicking. I find that shorter wicks are better for version 2, and a tiny bit of cotton on the juice hole for version 1 works well.
I generally vape around 18 watts when i have a single .4 coil inside the tank. I space my coil as it works better than a micro coil.