it isnt too difficult, can just be a bit frustrating and time consuming.....if its a small area you dont need power tools, but a DA is great
just make sure you've put hardener in the filler and let it go off.....when mixing try and get all the bubbles out as these have a habit of re-appearing in what you thought was a nice smooth surface!
try and get the centre of the repair/filler lower than the rest as its easier to make this up with paint rather than it being too high.
then paint a rough guidecoat over so it looks like fleck paint to see how it looks, flat back and start with primers!
see...piece of piss