I use a homemade solar wax melter: get a styrofoam cooler (you will not need the lid), a tall plastic bin that will sit inside the cooler, a regular sized paper towel, a rubber band and a sheet of glass (can buy one from a big box home improvement store) large enough to cover the top of cooler.
This needs to be done on a hot day, in the 80's would be ideal.
Put enough water in the bottom of the plastic bin to about an inch of depth (this is what the clean wax will drip into and the water keeps the wax from sticking to the plastic allowing for easy retrieval of the resulting clean wax block). Put the paper towel over the top of the plastic bin and use the rubberband to strap the towel around the edges. It is important to fasten the towel well. Take the wax you want to melt and press it into a patty that will fit onto the paper towel. Set the bin into the styrofoam cooler, put the glass over the cooler and set it into a space that gets sun pretty much all day.
At the end of the day you will have a beautiful clean block of wax in the pastic bin and a sludge of "slumgum" in the paper towel. I save the slumgum with the paper towel and use it as smoker fuel, it works really well. This sytem is super cheap, easy to put together and always readily available, the only thing I need to have at the ready is dirty wax, a paper towel and water.
I was planning on putting some pictures on my blog, I think this post will spur me on to finally do it.