Lee Hurd's "Visionary Guide to Lucid Dreaming" promotes Niacin at bedtime, not in conjuction with WBTB supplements. The flush is normal, but I would suppose that some people experience it worse than others.
That's amazing, congratz! Can you please tell a little bit more in depth about your WILD experience, how long time it took before you entered the dream, sensations etc? I'm trying it out myself and would love to hear how YOUR experience was.