While some cats are okay with being washed like a dog - using a spray nozzle - some cats totally freak out at the spray. I have bathed a lot of cats at the clinic, and have found they tolerate the "bucket method" the best.
You will need 2 (or more) tall 5 gallon buckets.
WITHOUT THE CAT PRESENT, fill each one with warm water. If you try to hold the cat WHILE filling the buckets, be prepared to call 911...
Bring in the cat, scruff it, and dunk it into bucket #1. (Don't ever dunk the head - just dunk up to the head. If possible, wet down the head/neck area before putting the cat in the bucket. Use a washcloth and flea shampoo/dawn - this keeps the fleas from finding refuge on the dry head - which they WILL do - they will crawl in ears and nostrils to get away!) You'll need to reach into the bucket to ruffle up the hair and make sure it all gets wet.
Take the cat out, apply soap, and suds it up. If possible, let it sit in a crate for 10 minutes or so, to kill the fleas. Be sure the crate is in a warm area!
Scruff and dunk the cat in the 1st bucket, reaching in and ruffling the hair to rinse it. Dunk it in bucket #2 to rinse it further. Rinse the head/neck with a washcloth.
Dry as best as possible with a towel, and return to crate to dry. You *can* put a heater in front of the crate but be VERY VERY careful that you do not overheat the cat! It does happen! If you cannot constantly monitor the temp in the crate, you are better off putting the crate in a small room (bathroom?) and heating the whole room, with a plain old fan blowing some air into the crate.
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*Dunk the cat slowly, and you might need extra hands to detach legs from the edge of the bucket.
*Use warm water - it seriously seems to make the cats relax like they are in a spa.... One of mine enjoys it so much he will willingly stand in the bucket, without attempting to eascape.
*Do not use Hartz or Bio-Spot or any othe "off-brand" flea drops on cats. Cats are extremely sensitive to chemicals, and can/do have lethal reactions. Do use Advantage, Frontline, or a fipronil containing product.
* You will need to treat the house, and/or yard, and any other animals in the house. It can take up to 3 months to entirely rid the house... So be patient, and keep killing the little buggers according to the directions on the package you choose to use.
*Sometimes you can find exterminators that have a gaurantee - if they can't kill the fleas in X# treatments, then the following treatments are free. Sometimes this can be cheaper and easier than do-it-yourself products.