To get to Woodhull Lake, you have to take McKeever Road from NY 28 in McKeever (1/2 mile before it crosses the Moose River, then drive back about 6 miles on a dirt truck trail known as Wolf Lake Landing Road. You put in at Wolf Lakes Landing, which is named after one of the lakes that Woodhull Lake covered when it was dammed up to form a larger lake to provide water supply to the Erie Canal.
While the road is fairly well maintained one-lane gravel truck trail, one creek crossing is a bit eroded from the rains of 2011. There are roughly 6 designated roadside campsites along the road, with minimal to no facilities that you can camp at. You can drive all but an 1/8th of a mile up to Woodhull Lake, where the road is gated off, from there you have to carry your kayak or canoe to the lake on the gravel road. Consider using wheels on your kayak to assist on this portage.
Here is a map of Woodhull Lake. Consider clicking on it, for a high-resolution map that you can print up, put in a plastic bag and use on the trip like I did. It works really well like this, and I think this map prints out to be nice and high resolution, especially if you have a color printer.