I would highly recommend not using a ND grad filter, instead, put the camera on a tripod and shoot some bracketed frames, then blend them together in Photoshop. You don't have to worry about aligning the filter with the subject, and if your tripod is rigid enough, the frames will line up exactly. Use aperture priority or manual mode and do a 3-shot bracket 1-2 stops apart, depending on the subject. Michael posted a handy tutorial on blending exposures, and there are many other places you can get instructions on how to do this.
BTW, the distillery shot on the front page is a blended exposure. Try doing that with a ND grad filter!