How do I find shelf fixing holes after skimming?

[tonefive]

Hi all
I plan to get my lounge skimmed by a professional (not me). Prior to the skimming I'll need to remove 6 shelves from the walls. I want to avoid having to re-drill the holes for the shelf brackets after the skimming has been completed (the walls are hard and the neighbours don't like loud drilling). Is there a way that I can find the original holes after after the skimming so that I can re-use them for replacing the shelves?
Thanks

 

[ree]

You could leave the screws sitting proud and loose in the plastic plugs, and the plasterer could work with them or suggest something else when he arrives - its no big deal.