Hey Niall, I also used Hammered Silver when I painted my light too, it's a little hard imho to apply because if too much is used then the texture of the paint will come out a little odd looking.
As for how I restored my light:
I first disassembled the fixture the fixture completely (some of the screws might be tight and make a diagram of how the ballast was wired before taking it apart) and took out the latch before sanding and painting the fixture, I also recommend you the take off any labels if they come off easily or tape them over with masking tape.
I then used a combination of a sanding pad and a electric palm sander to sand mine with around 80-150 grit paper but a random orbit sander might be better. After sanding, I gave all the parts a wash with a hose to wash off the sanded off dust and left it to dry before painting. You could also sandblast the parts and body if you have access to a sanblaster.
For the paint, I used a layer of spray paint metal primer first which was followed by two if possible, coats of Krylon Hammered Silver as I mentioned as the paint. I just painted the parts on the ground covered with old newspapers but I think using a workbench and a drop cloth might be better. I recommend that you paint you fixtures on a sunny day and outside so the paint drys quickly.
When I painted my light it stunk for the first week or so I would leave it in the garage until the smell dissipates. Sometimes turning on the light and making it heat up will also release the smell even after a week.
Now finally after everything was dry and the paint cured, I put everything back together and unasked or stuck the labels back on and had fun turning on my repainted light.
You should be able to buy the paint at either Canadian Tire or Lowe's.
Good luck and have fun with your restoration