Follow the
Master Wu technique for making Green Dragon(GD), Everclear would be ideal if you can get it around your area, Bacaradi 151 would be a good second choice if you cant find any Everclear. If you actually read through Master Wu's entire thread you will notice he mentions that he is a "lightweight" and only needed 1 drop to feel the effects, your mileage may vary.
This thread suggest using a mixture of 50% VG and 50% flavouring(The Cola flavour is really starting to intrigue me). Personally I would start off by using 50% VG, 25% flavouring and 25% GD. Use that as a basic recipe and adjust as to your liking. VG is a very thick liquid and your final THC solution should be more on the watery side after mixing/diluting with flavour+GD. Many people use a small bottle with an eye dropper as a convenient mixing/carrying around bottle.
CaSHMeRe suggest buying this brand of VG,
Nature's Answer Pure Vegetable Glycerin, ive found this product on ebay as well as this online store:
VitaminShoppe
Some people have tried using Marinol(spelling?) in an e-cigarette with little success. Marinol is man made THC in the form of a pill if you are wondering. A lame attempt by the Pharmaceutical company's trying to cash in on MJ's healing properties.
Some people have made tinctures by just soaking finely ground up bud in VG for 60 days. You could try this method as well but for me it would be too time consuming. Also, I have read that VG can only absorb up to a maximum of 30-50% THC before it is saturated. Alcohol on the other hand can absorb 70-100% THC depending on the alcohol content. I couldnt find my source for this info but I remember reading it, so take this with a grain of salt.
Im not sure on the chemical properties of BHO but from looking at video's and online pics it looks as if it would be really gooey and gummy. As stated earlier, oil based products arent recommended as they gum up the atomizer that vaporizes your solution. With that said, this method does have the potential to work but we wont know for sure unless someone tries it.