I suggest shutting thermostat to off keep it off overnight(this will allow coil to thaw). Then turn unit on in the morning and let me know how the air flow is. Spraying off outdoor unit is a good idea, but plugged condenser usually does not cause freezing. If filters have been neglected at one time or another, your evap coil may be plugged. Your best bet is to have a pro in to check system and determine cause of freezing. Make sure to have them explain what the problem was, and if it was an easy fix, maybe next time you can fix it yourself, or prevent the problem with do it yourself maintenance. And if the problem was of a bigger nature, you will know that the money was well spent by having a pro into find and solve issue.
I suggested checking filters as an easy do it yourself fix, beyond that, it takes an extreme knowledge to trouble shoot an ac system. Good luck and please let us know how things work out.
PS. if tech finds a low refrigerant charge, make sure that they have found the source of the leak and fixed it.