I'd had issues with using rattle can paints. Typically, my finger would pick up a bit of paint and it would drip down on to the work. Plus, the effort made my finger tired.
I tried this product, which I got for a few bucks at the local hardware store:
What a difference! It holds the can firmly and it's easy to use. This is the right tool.
Strongly recommended if you use rattle can paints.
Also, I got a pack of replacement spray nozzles for these paints. The ones that give a fan-shaped spray give better coverage and use less paint than the factory nozzle, at least for Tempo's Zinc Phosphate primer.
Together with the handle, these made a big improvement.