It doesn't need to be totally wet. The moisture just makes getting the airbubbles out pretty easily. I use 70% isopropyl alcohol and water instead of soap becuase if you use too much soap, it'll take forever to squeegee all of it out.
Take a starndard size squirt bottle (32oz) and a 16 oz bottle of alcohol, pour in 1/2 the alcohol(8oz), and the rest warm water.
Masking-tape up where you want the vinyl to lay, then peel the liner back, spray the vinyl surface and the car too for just a decent mist), lay it down where you want it (you can peel it back up) and then squeegee it down firmly, pressing all the liquid to the edges. The alcohol/water mixture will allow you to get all the bubbles out very easily, and when you've squeeged everything, just peel off the tape and you'll be done,

It dries very quickly. Use a safety pin to get out any left over bubble under the vinyl. Good idea to claybar the area first, it'll remove any road debris as well as any existing wax you may have there. Good luck!