In my humble opinion one of the best ways to get a PB on your 5k is to use a human pacer.
I find that looking too much at your pacing-watch makes you lose focus. Don’t get me wrong they are great for training but not for me in the race.
The problem with human pacers though is that they are fallible and will often run a little slower than they should – despite being able to run much faster should they choose to. There are a variety of reasons for this including the fact that: they don’t normally run at this speed; as well as that they themselves are probably using a pacing device and that will not give an accurate reading unless they run in an exact straight line around the course ie their 5k probably ends 20m before the finish because they deviate from the very shortest route.
So use a pacer BUT make sure to stay ahead of them. Or move ahead of them in the last Km or two.