The valve turns! help

[JenTay]

the car started to run funny yesterday and it was clear i had to redo the valve job i did a couple of months back (maybe it was not tight enough or whatever reason).

in any case i can't seem to loosen the lock nut on one of the valves. the whole blasted valve turns. the ************** manual says jam a flathead between the rocker arm thing against the six sided valve thing. i assume that is the flat thing on the top of the valve. when i jam a flathead in there and turn the nut, it does not work. it is too slick. i know there was a third tool that is sold along with the bent wrenches but everyone seemed to say it was unnecessary.

is there a trick to this jamming the flathead in there? or am i destined to buy that other tool. help!

jts