I have never rendered lard, but I have rendered suet into tallow in the oven. I put a single layer of paper towel in a colander. After pulling everything out of the oven, I pour it onto the paper towel. Then you can push down on the cubes with a wooden spoon to squeeze out more of the rendered fat. That helps me get a lot more fat. If your bowl isn't much deeper than the colander, then as soon as the liquid in the bowl hits the bottom of the colander, dump it out and squeeze more.
Also, to your question, for beef, you get ~60% yield. So 2 lbs of suet would yield 1.2 lbs of tallow. Lard may different, but likely in the same range? What remains is cracklins:
So when they look like those pictures, you're done. I think if you keep temperature low, you can let it go longer in the oven. I don't think there is a risk of burning, but I could be wrong. I would just keep going until it doesn't look like things are changing anymore.
By the way, this doc has good instructions and lots of pictures:
I can't remember where I read the 60% yield, but my own experience has matched that number.