Spray can trigger handle. My gawd does my finger love this little device. Every workshop should have one. Primer, paint, clearcoat, bugspray, polyurethane, silly string, barbecue paint, carburetor cleaner, anything.
I just hit Home Depot last night... TWICE (Don't ask... ugh) and they've got these can triggers in their painting area, hanging on the frames from those dangly plastic display thingies that everyone always seems to knock down. $4 here. It's invaluable. Great amount of control. Once you aim the spray nozzle straight out the trigger, it's far easier to accurately paint cuz the gun shape aims for you. Also less wrist strain, I've noticed last night.