Cabochon

How do I paste a cabochon gemstones in a vintage pressed glass pendant?
Do I need to begin creating abrasion or sanding first?

No. You should only have to clean both thoroughly and keep your fingers bare surface. Use Goop E6000 or related company creating silicone adhesive can be used as contact adhesives to enter quickly. http://www.mikegigi.com/glues.htm # E-6000