I have to disagree with you there MVC. I've brushed and sprayed this in large quantities. The spray is easier in large areas, like a bench top. However I would use a brush for a mower, particularly if the budget is tight. You lay the paint on quite thickly and quickly for the second coat and the effect is the same as a spray. It would also be faster than a spray, by the time you thin the paint correctly and clean your spray gun afterwards.
You are right about the spray tins, you can still buy them and they are insanely expensive.
At a guess, you might paint 2 mowers with a tin. Tins would be very fast too.