I don't have an opinion on the product you mentioned. I am not sure how well it will break down the debris that gets down in the tight slot of the evaporator housing.
I just had to have the evaporator changed out on mine. Took the mechanic 7 hours altogether... it was a tedious job. He did it at my house, so I knew he did not piddle- I watched and helped out (taking the dash out of the truck). I had him change the heater core too, even though it was not bad yet, since everything was apart to get at the evaporator. The heater core is right next to it. Most of the cost of this job is the labor involved at getting at the parts. He showed me where the evaporator was leaking; there were leaf fragments and other debris down at the base of the evaporator, and that caused it to corrode.
I am going to install one of the fresh air vent filters from Geno's garage in an attempt to keep the debris from coming down the vents in front of the windshield and thus damaging the evaporator.