I agree with Ole Annie, dont risk using salt water. Besides, when experiemnting change one variable at the time...not many. If the tonning does not work you wold not know if it was because of the salt water or not.
Mixing pt ot Pd is very simple, it is not dangerous other than the posibility of breathing the stuff. If you do it in a well ventilated place you should not have problems, after all you have to do is mix water, pt ot pd and salt...:P
The one thing that has helped me get the pt ot pd in solution is heating the water to about 100 ºF.