Wedding Dress Correct exposure?

I would like to know what camera settings should be used in different lighting conditions to ensure a wedding dress is correctly exposed. I understand the plus 2 stops thing for spot metering in Manual mode when their is heavybacklighting to ensure the dress does not come out grey. However in low light conditions that does not enable plus 2 stops of exposure in manual due to a slow shutterspeed how can i expose the dress correctly. Would i be right in saying that in dark conditions it is ok to use aperture mode and evaluative metering and underexpose as the camera meter will be metering for the darker areas making the dress run the risk of blowing out. Also when metering +2 stops on white it only exposes correctly when no flash is used. When i use flash -1/2 stop in ettl the detail blows. Does this mean that if metering +2 in camera i will need -2 flash to get the correct exposure.
james
james

White will always be white and will always have the same effect on the meter regardless of the ambient lighting. Changeing the metering mode will not suddenly give you a higher shutter speed, that is what the ISO setting is for.
A little trick, hang up a white sheet in a room and throw a piece of net curtain over it and try to get a metering mode and setting between flash and camera that works for you which retains detail and stays white and then you can come back and give us the answers, after all practice makes perfect.
Mike
A little trick, hang up a white sheet in a room and throw a piece of net curtain over it and try to get a metering mode and setting between flash and camera that works for you which retains detail and stays white and then you can come back and give us the answers, after all practice makes perfect.
Mike

I have been practicing on a textured bath towel in manual +2 stops with -1/2 stop flash and when using flash the detail blows. Also when doing this inside with little light in th background it exposes correctly without flash but the background is virtually pitch black.when i use flash it exposes the whole image properly but blows the detail in the white. james