A human being could turn an oven on at 350 degrees, stick their hand in it and not burn themselves. But only if they first prepare their nerves for the heat. The original method is to dump warm urine on the hands. However, we live in the modern age. Takeing a warm shower shall suffice.
Heat travels faster in water so please be careful of the tempature.
Basically, don't tense up. It will hurt more. Start at a tempature a little hotter than you usually take a shower in. Gradually over a month, gradually increase the tempature of each setting. Try to work each area seperatly.