I have an Aplliance Parts Warehouse by me and they sell everything AC related. Great place. Never seen a pressurized can of Microbial cleaner before except the dealer stuff I quoted. I see alot of pressurized Coil cleaners but no micro. And alot of micro cleaner in a jug to use in a bug sprayer. Plus without the special hose that comes with the dealer cleaner can it would be a rube goldberg deal for sure rigging up something to inject it back up the condensate tube. The special hose is part of the $25 expense. The dealer hose works really good and fits well. You can let go of the can and it stays hooked. That treatment works really good and the car smells great for about 9 months. if I had the patience to do the vent/blower deal at the end of the drive it would last a long time but to impatient for that.
Does the black plastic cap w/hose fit on top of where the spray paint type nozzle would go (on the little tube)? Anyways, just FYI, they sell the foaming e-coil spray at Grainger if you live by one.
I checked Grainger and they have foamy cleaner but without that hose adapter its pretty useless. It has to be an airtight connection for the foam to go all the way up the tube and notice how big the hose is. It needs a big hose to push foam. I guess you could ghetto it all up and maybe end up with a face full of foamy cleaner or pay the $25 and it's done right.
A lot more comments about what other people used and some googling to see where it can be found and I thought I would tell people where they can find it. I don't think the dealer hose isn't anything but a vinyl tube (Lowes for $1) and a plastic cone at the end. I just wonder about the other adapter end for the can that might be what is needed. I'm wondering if you can also sneak that dealer hose in by the A/C line grommets or past the squirrel cage fan and spray the foam from the top.
I've been getting that musty smell too when the AC goes off or is on low. Maybe I'll try running it with the AC off for 5 minutes to see if that helps dry it out.