I do this on a lot of guitar necks. Like mentioned above it is a good idea to mask a line at the headstock and heel to keep it looking neat. I wouldnt use anything coarser than 0000 but youmay get by with 000, if you go any coarser you will regret it. If you have any problems finding wire wool that fine check out
http://www.axminster.co.uk, they stock it.
i usually apply a small amount of prepared beeswax (briwax) when rubbing with the wire wool because i feel it leaves it looking more professional.
It shouldnt take much work to get a suitable matt finish but be aware that your hand will re-buff the finish and it will get glossy spots sooner or later and you will have to repeat the process (probably annually depending how often you play), this is true of most matt finshes anyway.
Mask off any electrics to stop wire wool getting near them!
This process is reversable (good if you want to sell the guitar) because you can always rebuff the neck but if you have to do it often and find that the clear coat is getting thin it might be worth getting a few new coats of clear lacquer to make sure you never go through to the colour, although to be honest i think this would take years.
Incedently, on alot of the guitars i make i use an oil and wax finish on the wood which feels much nicer than gloss or matt lacquer
