Joe,
Last time I used a friend's ultrasonic we used tap water w/a squirt of Dawn dishwashing liquid. It was very effective in removing the crud from a trigger mechanism & some other gunked up parts. After removing them, we washed them off in hot tap water which actually warmed them up enough to dry almost instantly. We were fairly quick to re-oil the pieces so no rust could occur. If you do not have compressed air, I suggest you could use an inexpensive hair drier to good effect ... or at the moment just set the parts outside in the ambient temps for about a minute [hahaha] after washing them off in hot water. Too, there are the aerosol cans of dry air sold for blowing off dust on computer parts and key boards.
Best, tw
