I use tanning essentials ProV spray gun.
I have it set at either 3 or 4.
I am around 6 - 8 inches away from the body.
I use St Tropez, but recently been trying out Moroccan tan - and loving it.
Both brands dry instantly.
When I wipe around my tent afterwards, there is hardly any overspray....one wipe is all thats needed!
I do have the extractor that went with the kit, but to be honest, I rarely use it.
I find 40 mls is usually about right.
I do not however spray all day!
I think folk who do, are probably wise to get an extractor.