What is the ruling on the transfer of impurity from a wet garment to the body merely by touch, and must there be a visible trace for this to occur? And is washing the body out of fear of impurity transferring from the garment to the body, given temporary urinary incontinence, considered excessive scrupulosity (tanattu‘)? And does preponderant assumption (ghalabat al-dhann) apply here? And what are the references that clarify that impurity does not transfer from a wet garment to a dry garment except if a trace appears, along with their proofs?

What you are doing is according to the Hanafi school, which permits a layperson to follow someone whose knowledge and piety they trust. The Hanafi school holds that a dry body becomes impure if a trace of impure wetness appears on it. It is stated in the Hashiyat al-Tahtawi al-Hanafi that if what touched the body becomes wet, then it is impure; otherwise, it is not, and mere dampness is not considered. As Ibn Abidin said in Radd al-Muhtar: If the wetness of the bedding touches the body and its trace appears on the body, the body becomes impure. Semen is considered impure by the Hanafis, but the more preponderant opinion is that it is pure. Washing the body due to the impure wet underwear touching it is not considered excessive meticulousness (tanattu'); because it is considered impure by schools other than the Hanafi.