There are a few good products that we recommend to use to degrease your Persian cats coat.  One product (pictured) is Groomers Goop.  If you choose to use Goop to degrease your Persian coat, do not use any formula of Goop that has pumice in it.  The Goop with pumice in it will take forever to rinse out.  

If  you are not comfortable tackling such a big job, you might try degreasing your Persian coat with Dawn dishwashing detergent or House of AnJu One Step Degreaser. We recommend making sure that your Persian cat is comfortable with both you and the bathing process before even attempting to use Groomers Goop for degreasing.  

It is best to allow plenty time in your schedule if you are going to attempt such a project. Groomers Goop works best when it applied directly to a dry coat.  Typically for an adult cat you would use one entire container of Goop.  Please note that if you are attempting to use Goop for the first time, we recommend only a small amount of Goop to start  to make sure you are completely comfortable with the degreasing and bathing process.  We have found that if you heat the Goop in the microwave for approximately 40 seconds then stir it until it is the consistency of liquid it helps the application process.  It is VERY important to make sure the Goop is not too warm. If you get it too warm you will burn your cat.  Remember that your hands can tolerate much warmer temperatures than a cats sensitive skin so please be very conscious of this fact.  Once you have started to apply the Goop to the coat, work the Goop into the coat taking each hair rubbing it between your thumb and forefinger.  Work each hair from the root to the tip and vise versa.  You will want to also concentrate on the underarm, belly, ear, neck and ruff areas as these areas tent to be the most greasy areas of the cat.  During the de-greasing process your cat will look like a "Goopy Mess," this is pretty normal. Start working the Ivory onto the coat with the Goop, you will want to work it through completely down to the skin.  Work this for several minutes. Once you feel you have worked the Goop into each hair strand it is time to remove the Goop and start onto the bating process.  When you start the bathing process, it is imperative to get the Goop out of the coat completely.  The first time I used Goop to degrease my Persian, I didn't get it washed out well enough and ended up with a cat that had a coat that was as greasy as I started with.
 

If you are not comfortable using Goop Hand Cleaner for degreasing your Persian cat, there are a few other options.  Dawn Dish Soap or Ivory Dish Liquid.  This type of degreasing works either two ways, you can apply it directly to a dry coat in the same manner you would the Goop, or wet the coat and apply to the coat.  Once you have the dish liquid on the Persian coat you would work it with your fingers as you would the Goop.  

You can either use the dish liquid full strength or dilute it with water.  Both dish liquids work equally well in degreasing the Persian coat, however, we prefer Ivory Dish Liquid to Dawn Dish Soap due to the fact that Ivory Dish Liquid rinses out much easier than Dawn Dish Soap.