The salon where I did the Mystic Tanning said to exfoliate (with their expensive stuff or a plain old loofah) first...no mention of shaving. They did say to wait 4-5 hours before showering, but even after waiting overnight, and late into the next day, the color streaked. I definitely would not do it on the cruise. It rubs off on your clothing, if you swam, it would run (or even got sweaty- they did warn me about that) and it smells. They had me stand with my arms out to the sides, but after the 1st time or two, I found that I needed to move my head up a little to get my neck tan, and (kinda yukky) spread my legs a bit more to get the insides.
I think if you're young, and thin, with no lines or wrinkles, it may go on more evenly...if you get my drift.
I'm now doing the tanning beds, and like it much better.