Bushings don't give precision, they give a longer lifespan. You don't really need the lifespan gain here I think. A homemade drilling guide made even in pine can last well enough with care when using it, certainly should give long enough service to drill dog holes for a single bench. And if it doesn't just make two of them to begin with! It's just a few bits of pine
Also remember that you can reduce the wear and tear on a drilling guide by removing it once a certain depth of hole has been drilled. The start of the hole in the workpiece then becomes the guide to drill the remainder.