I must admit that I do not always wax the tip of grafted scions, to stop the scion from drying out. But where I feel its a necessity, I use a homemade wax mixture, and its heated up in a “Ladies Hair Wax Removal” heater. The one I use has got a temperature controller with a display.
As I use a mixture of candle wax, beeswax, and zinc cream, it can still produce quite a hard wax covering. Its only there for a few weeks, and the breaking buds soon push through it.