A double boiler , not broiler , is just a smaller pot nestled into a bigger pot with water being heated beneath . It cuts the risk of the wax catching fire to nearly nothing . A microwave would pose a lot bigger fire hazard , and your Mrs. is far more likely to be POed if you burn the house down than if you just mess up her stove .

You can buy a double boiler pretty cheaply in the housewares section of most Wally Worlds . Put about 1-2" of water in the lower pot , or just enough to barely touch the bottom of the upper pot , and keep the burner just high enough to get the water very hot but not boiling . Then put small chunks or shavings of what you want to melt into the upper pot of the DB , and watch it until it's completely melted , stirring occasionally .