I have a cheap pizza pan from wally world that I use as a diffuser. I drilled holes in it with a 1/4 bit. Normally I keep it covered with foil and change it every few cooks. With that in there I don't have any problems with grease getting on the coals normally.
I'm there with ya when it comes to checking the temps all the time. Over time though you will learn to trust the UDS and you will only check it on occasion.