For twist bits, i generally do them freehand. First, with the grinder off, i hold the bit to the grinding wheel to match the existing grind angle. Then i turn on the grinder and go to town. It's quick and certainly accurate enough for my purposes.
For forstner bits, i clamp the shank in my bench vise with the head up and use a fine flat file to dress the point and cutting edges. Make sure not to file the outer radiused surface. Always file the beveled edge, not the rounded surface.
Try one or two to get your confidence up. Look at it this way, if they're already dull and unusable, if you mess up the grind once or twice, you're certainly not out anything. I think you'll find that it's easier than it seems.
Good luck, and have fun with it.
Paul Hubbman