A very important thing to remember if going for dual (or more) coils - they all need to be EXACTLY the same resistance. As long as they are, the current will divide equally between them. If they're not, the lower resistance one will be drawing more current, you'll get one hotter than the other, and a poor vape. The greater the difference, the more the imbalance.
Think of a car battery, with the car running. You inadvertently touch the ungrounded battery post while your other hand is on the body of the car - and (most people! but don't try this on purpose, ymmv!!) don't get a shock. Why? You're in parallel with the rest of the load / resistance of the circuit. YOUR resistance is a lot higher than the rest. (Dry skin is, to 12 VDC, pretty close to infiinite. Wet skin, not so close.) So effectively ALL the current goes out to the rest of the circuit, and you don't get at all warm.
Think of a car battery, with the car running. You inadvertently touch the ungrounded battery post while your other hand is on the body of the car - and (most people! but don't try this on purpose, ymmv!!) don't get a shock. Why? You're in parallel with the rest of the load / resistance of the circuit. YOUR resistance is a lot higher than the rest. (Dry skin is, to 12 VDC, pretty close to infiinite. Wet skin, not so close.) So effectively ALL the current goes out to the rest of the circuit, and you don't get at all warm.


) the market dry.