If you're like me, your tools can get filthy from repeated use especially the candle holders. I sat down one day and thought to myself, "There has to be a way to clean all the wax build up." I wasn't about to scrape the wax by hand and I've tried. Depending on the design of your candle holders this can be a very difficult and often stubborn task.
What I did was take a large pot, big enough to place my candle holder and boiled some water. Allow the water to boil at it's peak before placing the candle holder. I wouldn't recommend doing this more than one at a time. No need to multi-task here. Now you need to use your own judgment at this point to determine how long the candle holder needs to be dunked in the boiling water. This can be dangerous especially if the candle holder is made of glass. Glass under extreme heat can shatter. My candle holders are made of plaster and the heat can quickly crack the design.
Use a pair of tongs to dunk the candle holder. Check it periodically until your satisfied with the results. Not all of the wax may come off. In this instant you can scrape off what remains in those deep nooks with a toothpick or other poking object which won't damage the candle holder. The was will still be hot at this point which makes it much easier to scrape off.