The problem is actually not that the paint is not sticking but it is not drying so the paints runs to the bottom of the globe. Heat can often speed the drying process and turning the glass ball to allow the paint to flow all over instead of going to the bottom of the ball will also help. The heat from a blow dryer like used for your hair will supply enough heat to speed the drying process. Blowing air across the opening will also help.
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