Airbrush makeup should be applied at low pressure, usually between 8-15 PSI. Raising the PSI is rarely the answer to restricted flow of makeup. Try expanding the hole in the top of the fast-blast cap to allow more air to be pulled into the bottle which in turn will allow better siphoning, or up flow, of makeup to the airbrush. Insert a marble or stainless steel washer into each bottle to ensure thorough combining of ingredients when shaking.