These are the answers we received from the offices of the maraje’ regarding your inquiry:

The office of the Grand Ayatullah Khameneni:

The sweat of a person who has become junub from a haram act isn't najis.

The office of the Grand Ayatullah Sistani:

The sweat of a person who has become junub from a haram act isn't najis.

The office of the Grand Ayatullah Makarem Shirazi

The sweat of a person who has become junub from a haram act isn't najis, the only thing is that one can't pray with clothing that is sweaty with that sweat.

The office of the Grand Ayatullah Safi Golpaygani:

The sweat of a person who has become junub from a haram act isn't najis, but as an obligatory precaution, one can't pray with clothing that is wet from it, and regarding your question, it isn't necessary to wash the hands.