You would sand it all down first, mix up some filler and fill any small holes wait for that to dry it will take about a hour/half hour then sand the filler down so all smooth with no bumps, then use grey or white primer spray one thin layer of premier on the panel wait for it to dry and sand the primer back keep doing that until the primer builds up to be a nice thick strong layer then start to spray the colour of your choice on the panel. Once sprayed your colour of choice on sand down with very soft sand paper wet and dry would suit the job. For the primer use about 180P grit and for the main colour use 400p grit which is very soft wet and dry.
The primer allows you to see any scratches or bumps on the panel surface and when your sanding down and spraying more layers on it will slowly fill the scratches.
My panels and mirrors were fu*ked when i got my bike so I had to do the same plus I have been doing body work for years!
http://www.ebay.co.uk/itm/2-X-500-M...lies_Paint&hash=item4837c1c48f#ht_2230wt_1163
There's some good spray i use, cheap and in a big 500ml can