Adjusting valves with cold engine

It's widely known that adjusting the valves on a slant six with the engine running is the way to go. Drop the idle down as far as it'll go while still running smooth. Pop the valve cover off and you should get zero oil spillage. I've done this about 10 times and have never noticed oil getting on anything outside of the head. I just use a 1/4" ratchet and short extension. Takes a second to get the rhythm but once you do it goes pretty quick.

One thing, I was adjusting my valves annually and the adjusting screws started to become loose, causing the valves to lose their adjustments far too early. Had to remove the rockers and hammer on them a bit to tighten them around the screws. Has worked ok so far but I would suggest adjusting your valves only when you absolutely need to. If you don't feel the "snap" when you initially turn the screw, it's probably starting to become loose and will fall out of adjustment earlier than anticipated.