Setting raw white balance in studio

Hi !

I sometimes use neutral density gels to lower the light levels of my Elinchrom studio flash units

and these can introduce a bit of a colour cast.

Am i best to use an 18% grey card or a white card to set perfect white balance (or something else like expodisc) ?!

What is the best way to set white balance in Adobe Camera Raw when shooting in studio ?

Advice appreciated !

Professional photographer specialising in people, places and 360 degree interactive panoramic imagery : www.rodedwards.co.uk.