use the de greaser on a warm engine, hose off lighlty... easy with a pressure washer, if its leaking oil out, you can blow water in..... most of the time, one can of degreaser isn't going to cut it , better get a few. Let it dry, move it to a location and put some cardboard under it, let it idle till you see the first few drops fall on the cardboard, shut it off and crawl under, inspect.
Take it for a short drive to warm up to full temp, get it back and put another piece of cardboard under it and look for the big leaks, only tough thing is going to be figuring out where it came from if the fan has blown it around.