This is a pretty handy accessory. I use it with Gary's Ultimate Dressing. The can comes with several different spray nozzles, I find it gives me better control of the spray than the pump handle, especially when doing my tires.
You just fill it half full of whatever liquid you want to spray and then pressurize it with your tire pump to 50 PSI.
http://www.harborfreight.com/cpi/cta...temnumber=1102