If I'm using silica I use 2mm silica for the coil wick, and two strands of 1 mm for the flavor wicks.
Here's an easy re-wick to try if you are not ready to dive in all the way (uses a stock coil, but new wick). Get some cotton balls (I use regular and boil then dry them). Take your protank head and pull the chimney off. Remove the flavor wicks and use some tweezers to gently remove the coil wick (probably easiest if the wick is dry). Put the head back on the battery and fire the battery a few times till the coil glows evenly. Take the head off and rinse any burnt residue off. Pull a wisp of cotton off the ball and use a doubled piece of wire or a needle threader to pull the bit of cotton through the coil. Use a needle or some pointy thing to adjust the coils if they've gotten wonky. Add another wisp of cotton for the flavor wick. Prime the new wick with some juice and put the chimney back on. This gives you nice clean coils and a fresh cotton wick and all you really need to buy is some cotton balls. I don't know that you'd really need to even check for shorts, since you'd be using a pre-made coil.