Tanning is just like nails, in that if you don't prep properly - the end result just isn't that good. A body that has been sprayed, but not properly exfoliated will go patchy. With an airbrush or gun, a tan is fairly easy to apply, and shouldn't really go patchy unless the person applying it is actually missing bits or it hasn't been properly exfoliated.
Different solutions will give different colours, last different lengths of time and in some cases fade differently, but I would honestly recommed you try out several yourself (if you are going to excel, you may be able to pick up some samples for your friend to try on you) and go with a solution/colour you really like. I went this the painful process last year of changing colour every few days and to be honest in some cases looked like I had either been Tango-ed or hadn't washed for a month. But it was all worth it in the long run to setlle on what I found to be the best solutions and systems.
If you want to look at the systems I decided on, I'm happy to run through them with you, but as a distributor now, would rather do that off-line, so feel free to pm me if I can help.
Lyndsay x
