Multiple flash metering

[J_S]

How should I correctly use a flash meter with mulitple flashes? I've just got my first flashmeter and radio slave flash setup. Lets say I have one flash each side of the subject, each facing the subject, angled 45 degrees from the angle the camera's pointing at. Am I right in thinking I need to point the flashmeter at the camera from the subject's position and take a flash reading from both flashes at the same time? Or each flash at a time? Or point the meter towards each flash and take the readings one at a time? What if the flashes change to 90degrees (so they're facing each other, with the subject in the middle)? HELP!!

My equipment:
-Canon Eos 5 film body inc. VG10 grip
-Sekonic L-358 light/flashmeter + RT32 radio transmitter
-Pocket Wizard Plus transmitter + 2 receivers
-Canon Speedlite 540ez + 420ez flashes

 

[Hertz van Rental]

You need an incident attachment - it's like a white dome. You should have one with the meter.
Hold it where the model sits and point the dome at the camera lens making sure you don't cast any shadows on it. Then fire all the flashes together.
This will give you the average reading for the subject. The dome attachment takes in all the light that will fall on the subject and then gives the equivalent of a grey card reading.
If you have a reflected light attachment you can point this at the individual lights in turn to find out the balance. For example, you might have a key light and a fill in. You want the fill to be 1 stop down from the key. You can check this by this method.
But you will still need to take an incident reading to get the actual exposure.
If you don't have an incident attachment, only a reflected light sensor then put a white card where the model sits and take a reading off this. Reduce the indicated exposure by 3 stops for B&W or by one-and-a-half stops to 2 stops for colour.