It is not something I do every session but at least once a season. We are in a tidal area where rotting seaweed makes lots of tannin, along with mud, making for dirty kites. In this case, I just got a great kite from a young lady out in CA. It's a F-One Rival 12M and not only came a little dusty ..but all new-to-me kites need a serious inspection.
There is only one real good way to get an even spread of soap on your kite: a Foam Gun. It premixes the detergent with air and makes something you want to run and slide on or find a lady to wrestle with.
The detergent is mas importante. I use a combo of commercial car washing soap and a high Ph mildew and stain remover. Afterwards, I usually spray the kite with 303 Protectant or some sort of water proofing. I learned about the water proofer after putting a PL flying pillow in the water a couple of times.
Not only does a clean kite look better in the sky - it gets all crispy again. N-I-C-E.
You know about dry, eh? Roll up a saltwater-wet kite and leave it for a year, no real problems...but rinse a kite with fresh water: make damn sure you let it dry. These are cheap plastic clamps with nice protective tips.
j i m