If I'm cleaning one at a restaurant, I go to the mop sink and hook my hose to the hot water, I have the foam gun that hooks to a water hose.
CY: I've considered the garden "weed and feed" dispensers, for the end of the hose.
You can also use the foam gun on the inside condensers if you have a big shop vac to pick up the water, it gets the floor real clean too.
CY: yes, I've used alki form for indoor condensors. Works well in restaurants. Needs shop vac or mop and bucket.
Be careful of the electrical boxes, I had a goofy general contractor use oven cleaner on a make line. The cleaner got into the terminal box and shorted out the wiring.
CY: Alki foam will eat aluminum, if left on.
Johnstone Supply sells a product called "4-X Base Coil Cleaner" that is very concentrated and will remove the most stubborn grease especially if you use hot water.
CY: I've used th at.
I've mixed it in to a washtub full of water, dropped electrostatic smoke eater elements into it and watched the brown crap just float off the filter.
CY: Also takes the tar and nicotine off evaporator coils. The smoke eaters are popular with some fire departments near me, for the bingo hall.