Just used the smoothrite black spray on my rear peg hangers and top box plate - lovely job but slow to dry and needed help with a hot air gun !! Also used the smoothrite silver spray (good match for the BMW ali silver) on the back rack - again nice job but needed lots of hot air to get it to cure. The spray can seems to me to be quite high pressure and is hard apply lightly enough. (top tip, warm the can of spray to room temp and warm the item to be sprayed) When I have used the brush on it cures way faster and is better for small areas (chips/scratches)
Even though they say to apply on rust, your finish will only be as good as the base !
Good luck