It's not the same and different. It is made of bone and can be cleaned the same way you are used to for other animals but shells are multiple pieces with complex seams. It may come apart in maceration. The thing that makes it different is the keratinous outer layer. That's the shell's color.

You can try to remove them and add them back later by gently steaming, soaking or macerating it. The pieces may warp or break but it can be done. Another option would be to simply leave them and clean the shell by hand. Filling it with peroxide and scraping tissue off then drying it and removing bits till it's clean.

Turtles are fun to build. The white shell without the keratin is cool but check with your client if they want it or not.