You can get them from QVC and I think from Sephora.com, and probably Kate Somerville has her own site. I'm fair skinned too, and one use really takes the edge off that stark white color. If you want more, just do it again the next day. You won't get too dark from just one, though, for sure. It won't rub off, as far as I can tell, but I usually use it when I get out of the shower in the morning (usually on the weekend), and then I just put my robe on until I'm done with my hair. After that, I get dressed, and I've never had it rub off. The tan slowly develops for about 4 hours.
With whatever tanner you use, be sure to exfoliate first, particularly dry areas like elbows and knees. Otherwise, you will get dark spots there. I would recommend using an exfoliant without oil in it, such as Philosophy hot salt scrub. I also use a Clarisonic Plus with the exfoliant.
For me, the tan lasts about 6 days.
One towelette is just enough for your whole body. I always start with my legs because they're the most white, and that way they will get the most "juice" from the towelette. Then I do arms, chest, then face.
The first time you might miss a little bit, so best not to "experiment" before an important event. You'll get it.