Enabling sFlow on HP 2800-series switches

Hi,

is anybody using the sFlow capability of HP 2824/48 switches? If so, I'd
be grateful for any information about how to actually enable and
configure sFlow on these devices. There seems to be no information
available on the HP web site and HP themselves were unable to
successfully demonstrate how to do this...

Thanks in advance,

-- 
Mike Zanker
The Open University
UK