hi, my name is XXXXX XXXXX I will try to help you .
what did you take off the car to get at the plugs.?
did you plug everything back in that you disconnected and took off ?
ok, do you get a higher idle when you first start it cold and then the idle goes back to normal ?
is there a check engine light on ?
the oil fouling is most likely a result of the valve cover gasket leaking down in one or more of the spark plug towers ,on the cover gasket there are 4 gaskets which stop the oil from leaking into the spark plug sockets,these get brittle and dont seal .
you should have a fater idle at start up when it has sat over night and when it has sat to cool down then the idle should return to normal .
when you took out the plugs was thre a lot of oil in the spark plug tunnels?or on the spark plugs ?
I maybe suspect since you say it has a little rough idle for a min or so that the oil is still leaking down on the plugs or a few of the plugs ,
starting fluid may be helping because it is raising the flash point of the spark plugs or rinsing off some of the oil .
it may also be good to see what the coolant senor temp is reading when it is cold