0.2495 is good for a tight press on a 1/4 dowel pin, 0.250 will still normally give a light press fit. 0.251 is a good tight slip fit. Dowel pins are normally on size to + 0.0002
Drilling 1/64 small is correct, then ream. I normally bolt the parts together, align everything, then drill & ream the dowel holes through both pieces as a final step. I would normally use a 0.250 reamer and drive the dowel pin in with a hammer. This works fine as long as the dowel pin hole is through the work, so the dowel pin can be driven through if needed. If it must go into a blind hole, then 0.251 would be good for removal. If inserting into a blind hole, cut a small air relief groove along the side of the dowel pin to relieve the air pressure, it doesn't take much. The dowel pin acts just like (is) a piston in a cylinder.