I have actually never had my self tanner fade away all blotchy.. but it happens to some people. I don't like the tinted kinds.. some of the lotions are okay but the foams and sprays tend to come out uneven on me.. plus they stain my clothes! My favorite is Neutrogena Micromist; it's an airbrush kind.
I think the best bet is to get something more medium colored to avoid the blotchiness. Nothing TOO dark.. plus you can always put several coats of the lighter stuff and make it darker. There are lot of good self tanners out there.. but they all work differently for different people. The one I use doesn't come out very dark on me, but on others they said it was a LOT of color, so who knows.
I'd also recommend showering and shaving and moisturizing FIRST.. then applying the self tanner at night before bedtime.. then if there is any smell or anything you can do a quick rinse off shower. I've found this to work best for me! I also smell them in the store to try to find the ones that won't stink me up! Let us know if you find any other good ones

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