There are two main types of orifices for dolls: removable (inserted) and fixed (built-in).
The choice between a fixed vagina and a removable vagina comes down to personal preference. Fixed vaginas are one-piece, while removable vaginas use a split insert that is easier to clean.
After using a removable vagina, you pull out a sleeve that acts like a thin Fleshlight. Then you just need to rinse it with warm water and soap, and wipe it dry. You may also need to wipe off any excess lubricant on the doll's labia. But this process is fairly quick and easy. You can apply lubricant to the outside of the insert to make insertion and removal easier. I personally recommend removable vaginas, but some people say they don't feel as good, for example because in some models the insert may not fit properly and will slide inside the hole.
Built-in vaginas are harder to clean. Some people use soapy water and a sponge on a stick to clean the doll, but others recommend taking it to the toilet or placing it over a bucket and rinsing the vagina with a douche. It then needs to be dried, which usually requires some kind of fan or pump (like an aquarium air pump) to ensure air circulation in the hole. You can also use a water-sucking stick to dry it, and some dolls now even come with a water-sucking stick. If your doll is silicone, you can also use antibacterial gel to clean it further. However, it is not recommended on TPE because it weakens the material.
If you have a built-in vagina, there is another option, using a female condom. These can be pushed into the vagina and then pulled out when you are finished, so there is no need to clean up. However, some people say that it doesn't feel as good, and sometimes female condoms break anyway, especially if you reuse them.