Studio flash, D70 and white balance

I have some paintings to shoot coming up and will use the D70 and film.


I've read the manual and it seems that setting a custom preset is done
with existing light and not with strobe. I know the temps of my
flashheads, umbrellas etc but the room I will shoot in has yellow
walls, a warm hardwood floor and other things to throw off color.
BTDT years ago and bought a color meter.

So I could shoot with the current setup and do one frame with a grey
card in it, then use the eyedropper in curves and hit the grey card
and save the curve.

Or can I set the grey balance at the time of the shoot with a preset,
if I can. Can I?

 

Custom preset can use strobe.

 

So while I've got the shutter release pushed down to sample the grey card I fire the strobe?

 

The camera samples when you hit the shutter release, so strobe would do it.

 

"So I could shoot with the current setup and do one frame with a grey card in it, then use the eyedropper in curves and hit the grey card and save the curve."

This won't work if your WB is on Auto. It could vary from frame to frame in Auto. Your best bet is to use Preset WB and set it using a grey or white card with all the lights/strobes firing. You can also use Flash WB or even Cloudy WB settings but they won't be 100% accurate.