Bring a pot of water to boiling using the stove or microwave while you prepare the wax. The water doesn't need to be at a rolling boil, just hot enough to melt the wax. Imagine you were heating up water for a cup of tea that you wanted to drink very soon.  Alternatively, you could heat the jar while you're doing the dishes. Run some water and get it as hot as you can stand, then soak the jar for a while at the bottom of the sink. Another option is to heat the wax on the jar using a hair dryer. Turn the hair dryer on medium and blow the hot air over the wax until it melts.  If you have multiple jars to remove wax from, try placing them into the oven at 180 °F (82 °C). Place the jars on a foil lined baking sheet and put them into the oven for about 15 minutes to melt the wax. Allow the water and wax mixture to cool off for between 15 and 20 minutes. During this time period, the wax will begin to harden slightly on the surface of the water, making it easy to remove.

How would you rephrase that briefly using Vietnamese?
Đun sôi nước. Để sáp nguội.