Cleaning A/C coils: DIY or hire a pro? (See March 8 update)

We do ours yearly. You can buy the coil cleaner at a hardware store. Spray and let it sit for a few minutes, then brush off. We use an old tooth brush so we can get to the smaller areas (i.e. bends in the tubes). At the same time lubricate the fan axle and apply armorall (sp??) on the plastic fan blade.