There shouldn't be anything alive on the evaporator ,drain pan or in the condensate line. Use a foaming, self rinsing, bio-degradable evaporator cleaner. I use nu-Calgon @ around 20 bucks a gallon. You can use it straight if your equipment is really dirty or cut it 1 to 1 with a gallon of water. I use a 2 gallon garden sprayer you pump up. I also install 6x6 framed insulated doors for access, or you can cut a hole and use a plate and screws to seal it up. The doors are normally used to inspect fuses on self closing fire dampers in duct work. Grainger is a worldwide source but you pay a little bit more.