Useless Speed Restrictions

Early in my days of IFR control, I was guilty of the same thing expressed in the title. What do I mean? I hear it spoken sometimes at work by other controllers attempting to avoid putting #2 into a hold at one of our smaller airports, as discussed in yesterday's post. He doesn't really know exactly how much to tell the next pilot to slow down, so he uses an intentionally vague expression like, "reduce speed a bit," or maybe something like, "slow down a touch." Neither of which are useful to a pilot, really. I mean, just how much is a "bit"? How is that indicative of a value that will help? I have tried to teach any trainees that I've had that if a speed restriction is to be issued, make it count. Give the pilot a number to work with. Personally, I am happy that some pilots will come back and ask for a value, forcing the controller to think a little more about what he just said. I don't know if the message was received, but hopefully it will be in the long run.