Blockage...So dismantling a DC-4 Rocker Arm Info needed?

Had louder than usual valve noise so I pulled the valve cover to take a peak. When the engine is running a RIVER of oil is coming out of the rocker arm cups for cylinders three and four,, and wahsing down by the push rods...
It is also coming out of the bottom of the rocker tee and running down the outside of the tube that supplies it.

Here's the problem, very little oil seems to be reaching the tappits for the for front two cylinders( the very occasional drop, the furthest tappet doesn't seem to be getting any...I watched for about five minutes).

Am I right in assuming that there may be a blockage?

If so, I assume that undoing the 4 bolts will allow the rocker arm to be removed.

HOW DO YOU GET THE OIL SUPPLY TUBE OFF? Once off. should I soak the arm in kerosene or use compressed air?

ANY OTHER HELPFUL HINTS?

ANY information would be a great help.

Thanks.

Greg