Hi - I attempted a full respray once last year, and it turned out to be unbelievably expensive and a total waste of time because the machine died unexpectedly just as I had screwed it back together!
I went to Wilko and bought some plasti-Kote cans of spray-paint. Although it was only a small toy I ended up using about two cans of white primer and one and a bit cans of paint.
You can buy the primer there. I believe you should use white if you using bright colours and grey if you are using dark colours. I tried spraying outside but the wind took most of the spary away and dust kept blowing onto the paint. Dedfinately spray inside if you have a derilict room and household full of people indifferent to the toxic smell of solvents.
Negativity aside the finished product looked really good, but is incredibly time consuming as I had to do several sections in parts with several light coats over the coarse of several days.
Wilko also sell an own brand budge paint, plus primer but I don't know what it's like. Reed Ghazala's book has quite a few tips for painting which are quite handy, especially to someone like me who has no experience of using spray paint.