Kapton tape is your friend for hot air. It's cheap and you can get by with scissors.
Tape out anything that you're not reworking, use tweezers and push down the edges against the board to seal as best you can, and then flux it and blow.
It'll hold things in place and wick away the heat from anything you're not trying to rework. I went from a near 0% success rate to near 100% with it.
To protect larger areas, you can use aluminium foil. It's usually best to hold the hot air pencil at a right-angle to the board; if you angle it like a soldering iron, the excess heat all goes in one direction and you're much more likely to blow off small adjacent components.
Tape out anything that you're not reworking, use tweezers and push down the edges against the board to seal as best you can, and then flux it and blow.
It'll hold things in place and wick away the heat from anything you're not trying to rework. I went from a near 0% success rate to near 100% with it.