A/C evaporator coil is dirty causing drip. U need a permit to buy coil cleaner. Over the counter substitute?

My central a/c coil was dripping condensation instead of rolling in to the drainage pan. I'm sure it's b/c the coil is dirty b/c I've watched A/C repairment spray the solution on it, rinse, and fixed the problem. Can I do this myself and what type of solution/mixture can I use. Thanks in advance.