I get a st tropez spray on tan for special events, and I am pale, and get the colour applied twice. St Tropez fake tans include alot of green colour, so basically this fades out the orange.
I wear the paper knickers they provide, and the hair cap. I don't wear anything else.
Do go home in I wear strapless bra, loose trousers, loose top and flip flops.
I think it is definately worth it. I usually st trop myself in the summer, but the result from a spray on tan is flawless, and allows you to wear anything since your boobs are tanned, your bum is tanned, your neck etc etc. The only advise I have, is only get a brand named tan like St Tropez. There is no point scrimping on it, if the result is anything less than perfect.
Best thing to do is give it a go when you have not got an event, and then you will know what to expect. I have had about 8 spray tans using the st tropez and have always been very very happy.