>>529902795
I do use them to slow down if I find myself butchering the overhead break, but less than I did in the past.
>if you're having to use them on approach you haven't slowed down enough
That's generally true imho, but if I'm very light usually prefer to keep the speed break out and keep N1 higher so I'm not constantly bumping on idle, kinda like with the DCS F-16. I have no idea if this is proper procedure tho. I've seen both kind of landings so I guess it's more of a "at your discretion" thing.
I always think that if I was in the real jet, being close to the landing speed in case something happened and I needed to quickly go around, retracting the speed brake and pushing the throttle would get me faster, quicker than if I had N1 close to idle due to spool up times.

tl;dr= I don't really know what the proper procedure is