More fire. Seriously. The black stuff should start to glow red then turn white.
Also what type of torch are you using? It may be that yours isn't getting hot enough. (Edit: the vector should be ok)
Also I found this method to work very well:
Yes, you want the nail to get red hot. The white ashy stuff that "seasons" the nail is actually a good indication of this since it's more apparent when it turns red hot vs clear quartz which is hard to see in direct sunlight.
Also real quartz should be just fine with these heat levels. Doesn't matter how big your torch is, butane will only burn so hot.
Skillet Tools is a legit company, their stuff should be fine if it was intended for dabbing. I like Boro but glass dabbers tend to wick melted concentrate up and away from the heat source.
I let my nail cool down between hits. If you want specifics, usually 200°F or under if I'm checking with my IR probe. I don't think this matters though... and it will obviously take more torching to bring the nail back up to temp the cooler it gets.