You may have thrown out gourds that seemed to be spoiled when they became covered with mold. Next time, wait...mold is just a sign the gourds are drying out. They are just getting ready for future use.
Freshly harvested gourds are about 90% water. When they lose that water, they dry with a tough, durable shell. But in the process of drying, your gourds will probably get moldy, and be generally unfit for human company. But don't throw them away, just handle them gently and put them in a dry, out-of-the-way place like a basement, garage, or loft.
If you want, you can wipe off the excess mold now and then; if a gourd shrivels, then toss it out, since that one really has spoiled; but if only molded, just have patience. It can take months for a good sized gourd to dry out. When they are very light (the seeds may rattle), let them soak for a while in warm water, and you'll find that the outer skin and mold will come off fairly easily with an ordinary kitchen scrubbing pad. Beneath that moldy exterior, you'll find a beautiful gourd! After it's dry, it's ready for furniture polish or paint; it can be carved or wood burned; or anything you like. With just a little furniture polish, the gourd is an object of beauty.
If you grow your own, the easiest way to cure gourds is to just leave them outside on the trellis to freeze in cold areas of the country; or put them on a rack where they can freeze and have air circulate around them. When dry spring days come, most of the skin loosens and cleaning is easy. However, the designs created by the mold will be missing and the seeds will not germinate well.
ŠJohn J. McClintock 1996
For more information, contact Gourd Central