I don't, and never will, build my own coils. I'm thinking of trying a Nautilus for my vapeversary treat, but in the meantime my favorite is the Anyvape Davide. It can be used as either single or dual coil, using the standard Kanger coils. I also like the mini protank and the regular protank with an added air control.
Personally, I was very underwhelmed by dual coils. Somewhat more vapor, no more flavor than a single coil, and they eat up power and juice. They are great if you like recharging your batteries twice as often and buying twice as much liquid for a very slight improvement in flavor.