Personally, I prefer that my customers dont get too fancy with cleaning filters, rather that they just do it regularly- Once or twice a month depending on filter cartridge size.
Using a regular garden nozzle working from top to bottom, spray the pleats clean. Dont use a pressure washer.
TSP (trisodium phosphate) rather than bleach is a better household filter soak- Cascade dishwashing crystals are also acceptable... as Wmccall has indicated, you need to rinse them out really really well.