3. Steamy shower - been doing this since putting on Screen Protectors back when I had my Palm Treo, generally just running hot water in a sink will do the trick. No, moisture isn't trapped underneath - just have enough humidity to keep the dust under control.
Correct, a sink full of hot water is nearly as effective, there's a lot less particle in the air in a bathroom in general, steamy or not, so it's better to apply there. The lighting in a bathroom is generally bright and direct as well, so it's easier to line transparent films on your phone.