If you have tried the C8 from Apoloe with VG liquid you know that it pretty well plainly does not work and will provide many frustrating dry hits. There is a vid from davsolomon C8 (Cryptonite) Review - YouTube which makes some inroads towards modding it for VG use, however I found it only partially improved things for VG and would especially not work if the whole tank was filled. Reasons that VG does not work very well in this device is that it is a much thicker liquid which compounds the following issues. It seems the pressure in the tank does not getting equalized very well as you vape and the juice has to make its way along the wick through a small opening over a slightly longer travel distance than other cartomizers, which overall is a harder task for a VG juice (just guessing).
Anyway, this mod has completely fixed the dry vapes. Effectively you will be drilling two 2mm holes perpendicular to the existing wick holes and running a second wick through these, so that the new wick will sit across the coil at right angles, bringing extra liquid to the centre of the coil. See the photos below. Davsolomon does a good job at explaining how to disassemble the unit, so watching the vid first should get you on your way.
I got the second wick out of a C2 cartomizer and other than that you need a 2mm drill bit and a drill. Easy!
SV400155.jpgReady to start. The tool bottom right (black skewer) is to help pop the tin can thingy off by carefully inserting it into the existing wick holes and levering up. Be very careful to not go in too far or you will damage the coil.