The Flash is for use with essential oils. Dry herbs can damage the coil and we highly advise against using any type of dry herb in your Flash. A variety of substances, consistencies, and flavors of essential oils can be used in the pen, as long as they are not overly runny, sappy or in liquid form.
Remove unused liquids in the chamber by heating the atomizer with no mouthpiece or chambers and tipping the pen over a paper towel. This will help the longevity of the atomizer, as no oils will be building up inside over time with proper maintenance.