You can use an old crock pot (with a warm setting, do NOT use one with only one setting), or a small potpourri warmer (even one with a candle, if you remember to start it up early enough), both available at most grocery stores or a kitchen specialty
shop. You can even use a microwavable bowl, large enough to dip your hand into. If price is not an object, you can buy a paraffin
warmer at most beauty supply houses, or some sporting goods stores and department stores. These are often quite expensive, but I do believe that I saw one recently for a very reasonable price (under $50). The most important thing to remember here is that paraffin melts at a very low temperature, and it will burn your hands if you have it too hot. ALWAYS test your paraffin before you stick your hand in it, and use the paintbrush to paint it on if you want to be absolutely safe.