yep I used a sand blaster with some crushed glass then gave it all a good wipe down with celly thinners......I know the hammerite tin will say use their thinners, but I have always just used celly to thin down all hammerite products I have used.
The gearbox was sprayed with a little cheapo gun exactly the same as this one
http://www.ebay.co.uk/itm/Spray-Gun-...ht_4325wt_1139
it's spray pattern is variable up to 2" so there is little wastage due to overspray
two healthy coats and looks as good as new, you are supposed to use a special primer for ally but I have never used it and have had no problems with paint coming off