Soaking should not be done before shedding, only after the snake has begun to shed. Soaking can remove the oils and actually cause a bad shed if done too soon in the shedding cycle.
Also, I would think that if the water feels warm to your wrist, it is too warm. Think of the temps that are good for your BP - low 80s to low 90s. Human body temp is 98.6. If the water feels warm, it is probably at least 98 if not higher. Too hot. I would aim for it to feel the same temp as your wrist, because skin temp is going to be somewhat lower than internal temp, so that should be very close to the right temp for the snake.
Other than shedding and dehydration, there are at least 3 more reasons people might be giving their snake a bath:
1) - Soaking can often cause the snake to defecate. If you suspect a constipation issue, a soak is a good first step. Usually, though, I think owners worry about this when there really is no problem.
2) - After a female has laid her eggs, it is common practice to give her a bath to remove the smell of the eggs, which is supposed to get her back on feed again sooner.
3) - Swimming the snake for exercise. I am not sure I've heard anyone talk about doing this with a BP, but it comes up in regard to corns sometimes. Corns will over eat and make themselves obese, so some exercise makes sense.