If you have the holes in the shaft facing upwards, but oil only dribbles from the holes in the top of the rocker arms, this would indicate that you have lack of sufficient oil flow from the block to the oil distributor at the center of the rocker arms.
If you had sufficient oil pressure to that point, oil would be shooting out of the top of the rockers arms.
I recommend that you investigate blockages below the rocker arm distributor.
