Many years ago I was trying to figure out how to dry our lavender bunches. I looked into renting a local barn, but they are few and far between around here. In Holland flowers are dried in very expensive vacuum chambers. This procedure completely preserves the color, but it is extremely expensive and dims the lights in the neighborhood when the electricity is turned on.
In desperation I made a call to UC Davis. I eventually got through to a cut flower expert who explained a very simple set up that many cut flower growers in the Central Valley had adopted. You cover a greenhouse in black plastic leaving the side walls open to allow plenty of fresh air to flow. You then set up a a simple trellis system using 2 by 4s. In between these you hang the bunches of flowers from small nails driven into other 2 by 4s laid on the tresses. It is inexpensive and works very well for our lavender bunches.