I'd recommend adding a specific tan for weddings if thats what you are going to do. Most spray tan solutions are a brown colour....this is a guide colour for ease of application. It can however stain wedding dresses....not something your average bride wants. Most tans still have a residue of the guide colour after the first shower, and most brides want their tan as fresh as possible.
Its not always, in fact not often, it stains a wedding dress, but can be very upsetting to a bride if it does....it appears to be down to the fabric of the dress as much as the solution, but the main point is, that it is the guide colour and not the DHA or Erythrulose (which is the actual tanning agent)that does this. So get a solution that doesn't have a guide colour as wellas you regular solution. Naturasun do one, but I'm sure so do other companies.
You need practise....lots of....at applying without a guide colour, but it is usually a lovely resultant tan.