Yes, it is actually pretty simple once you know the trick. Set up the grey card so that the lighting is as flat as possible. Rotate the mode dial to the WB position and then select 'PRE' with the main command dial. Then, use the secondary command dial and throttle it in either direction once. The LCD and the viewfinder should change to a blinking 'PRE' notification. At this point the camera is waiting for you to expose a shot of something neutral. I prefer manual focus, because AF has trouble locking onto smooth featureless surfaces. Fill the frame with the card and depress the shutter release. It will auto-expose, so you do not have to worry about shutter speed and aperture. If the camera got a good read, it will blink "GOOD" on the LCD, and "GD" in the viewfinder several times. If for some reason it couldn't find a neutral value it will say "NO GOOD." Rotate the mode dial back to exposure preference and take a test shot. The scene should look good now.
If for some reason you cannot get it to read "GOOD" try taking some shots of the grey card and viewing the histogram. If there is a lot of data outside of the 18% spike, there might be a shadow, light fall-off, or something else. A good spike is about -- oh, 2-3% of the width of the histogram on the camera. You shouldn't have much problem though. I am not sure what camera you are using, but the D100 seems pretty good at getting a reading. When I do not have access to a card, I often use the painted wall to get it close, which actualy produces a kind of messy histogram, but it still gets decent results. Good enough for RAW anyway (which can technically be just about as off white as possible and still be fully recoverable in Capture.)