Answer: I'm not sure you will be able to hold them as long as you would like to -- they become hollow as they dry out over time. The best you can do is to keep them in a cool dry place place, rotate them and check them periodically for rot. Clean mold off the outsides as it occurs and discard any that go soft.
The gourds we see in the stores are sometimes sprayed with polyurethane and sometimes rubbed with oil or wax to make them shiny. You may find the Gourd Artist's Guild FAQ at http://www.jkstacydesigns.com/FAQ.html helpful as you work with your gourds. Good luck with your project!
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