I did a old cheby van one time...lots of windows and came out nice actually. The first time I had done one. Just like putting a decal on actually or doing woodgrain on a wagon. Just use a lot of soapy water and squeegee it well.
I might try Mark I did a Prevost bus I had that I turned into a motor home years ago and looked OK.
Not the end of the world I could rip it off and try again.