You can pinch the drain side of the oil supply line to increase flow to the rockers. You can take a stone for sharpening knifes and smooth the rocker end that is worn at the contact point with the valve stem. If you have the rocker arms clean and the weep holes open you should see oil at the weep holes. If the rocker arm shaft is worn badly you might need to rebuild the assembly. There are vendors that do this kind of work. What kind of oil pressure do you have? If the oil pump can not keep up with pressure at the bearings you won't have a lot of flow at the rockers.

Steve H