Can't give a step by step for the 580 but on both the A700 or A900 I use the following procedure, this works for all significant dust I have encountered over several years.
you will need a quality lens blower such as a pocket rocket.
1.as a preventive measure blow out your camera between lens changes (every now and then). also the rear end of your lenses as they can carry dust into your camera body.
2. hoover out your camera bag
ok to remove dust first do item 1 above holding camera body facing down.
then enter cleaning mode (on the A900 and 700 its a menu item)
again with body facing down (as much as possible) carefully blow off the surface of your sensor . Be absolutely certain not to touch the sensor with the end of the blower as this could cause permanent damage.
keeping body facing down turn of camera this will automatically close the shutter and lower the mirror.
reattach lens and do some test shots.
there are more expensive methods with solutions and swabs but I find this works for me.
