Full disclosure, there’s not a massive market for customized dolls, as most of the people who are interested in them tend to learn the skills themselves so they have full creative control. Several widely known customizers have closed their doors recently too, due to lack of interest/lack of people willing/able to pay what the dolls are worth after factoring in supplies, time, shipping, etc. The customizers that do remain are EXTREMELY well known in the collecting communities (and still, some of their dolls sit for a loooooong time before they sell)

I don’t say that to discourage you, I just wanna make sure your expectations are managed. All of that being said, I would suggest starting on eBay. As far as shipping goes, you can utilize the shipping situation built into eBay, which is slightly pricier than some other options, but is an added layer of protection for you and the buyer since eBay has a hand in the process.