Take the lens and shutter off the camera. Make sure your plastic bag is water proof before you slip the lens inside it. Then set the bag in the water and after it get warm work the shutter over and over. repeat it reheated water until the lens works as it should, then do it again a couple of extra times. You dont want it to get stiff again when it cools off. That should work.
Try that before anything else.
Getting the lens and shutter off the camera is pretty simple. With the camera closed open the back then find the spanner nut. There might be two the larger one holds the lens onto the camera frame. If you have a spanner wrench use it to remove the lens if not....
Get a jewlers screw driver set and a small hammer. Take the largest flat screw driver and set it at an angle(so that when you tap it gently you will be loosening the bolt. lefty loosy.... when you get the nut off open the camera slowly and behold you have the lens in your hand.
If you take the rear lens element off, you wont get any lens condensation build up. That happened to me just once but it can happen. The rear element comes out with the smaller spanner nut. It actually is the rear element of the lens usually be damn careful loosening it.
This sounds harder than it is. If you get the rear element off and the lens won't free up with the heat thing, go to the naptha that'll get her unless a spring is broke but usually if that it the case the shutter wont stick it just wont work.
Im sure there are others who can add more but in at least the last ten lenses and shutters I have NOT opened the shutter at all.