Or just throwing some incendiary grenades about.
There's also the notable goof that the Smartguns in Aliens and so many video games wouldn't actually be able to track the Aliens, because they have no IR signature - Predators can't see them with their normal sight and Dietrich looks right at one (whilst wondering aloud if they might not show up in infrared) just before the Hive ambush and doesn't see it.
You could argue in Aliens Vasquez and Drake are just spraying and praying rather than locking on, but in numerous video games at least the gun tracks Aliens flawlessly even though they should be invisible to it.