Now that you've invested in a sex doll, one of the most important things you can do is extend its useful life by taking care of it. And that includes cleaning it when necessary. It's important, but it's not overly complicated. You just need a few basic cleaning items and some consistency.
How to clean the outside
I've handled thousands of dolls and my recommendation is to give your doll a sponge bath or a quick dip in the bathtub. As long as the doll isn't heavily soiled, all you will need is some soap and water and a sponge or wash cloth. Wipe the doll down wherever it is visibly dirty.
If there are grease stains or smudges that won't come off easily with soap and water, just dry the area and then use baby oil and some paper towels. It's like makeup remover and it will remove almost all smudges that aren't permanent.
Now that you've cleaned the doll you may want to make it smooth again. To do that, just apply some baby powder and dust it off with a microfiber towel. It's that easy.
How to clean the inside
The basic concepts are the same for the inside as the outside, just keep it clean and dry. The only difference is that you will need a tool to be able to clean and dry the inside properly. The tool that I recommend are 12" locking medical forceps. You can buy them online at places like Amazon for just a few bucks such as here:
What you do is cut a sponge to fit the opening. For example a thicker sponge for the pussy and ass and a smaller sponge for the mouth. Soak the sponge in hot soapy water, clamp it into the forceps, and then clean the hole. You can clean it as much or as little as you need, depending on how dirty it is.

When you're done you can run the sponges through some clean water to rinse out any soap, and then use paper towels with the medical forceps to dry it out. When I'm done I usually roll up some paper towels in the shape of a tampon and then let them sit overnight to soak up any residual moisture. The important point is that you never want to let the doll sit wet inside, to avoid mold or mildew.
Some people ask me how often to clean. The answer is it depends on how dirty you are. If you're tossing the doll on the ground and cum in inside of it multiple times without using a condom, well then you better be cleaning it pretty often. If you're keeping it in a clean dry bed and not nutting inside, well then you don't have to clean it very often. Just use common sense on that one.