Place the pumpkins on a tarp and spray-paint them with the brilliant metal paint. Let them dry.
Check that the lights are working and then remove all the bulbs from their sockets. This will make it easier to thread the strand through the pumpkins.
Starting with the bottom pumpkin, pull the sockets through the holes and then screw on the bulb to keep it in place. Make sure you leave enough of the strand to come out of the bottom of the pumpkin and plug into an extension cord or outlet. Work your way up the pumpkin and then come out the top and move into the next pumpkin. Leave some wiggle room in between.
Wrap the pumpkins with crystal strands (cut to size if necessary) around the bottom, middle and top to give the topiary a little extra glamour.