I apologize that it has taken so long for you to get an answer to your question. Different experts come online at various times. I just came online and saw your question.Unfortunately, hairless rats are very prone to developing skin problems of all types. Fur on rats gives protection from dirt and bacteria, and the rat's own oils, which are meant to be spread through the fur. What you have described sounds like a case of the rat's own skin oils hardening. This can be the result of dry air.
No matter what is causing the problem, there are some steps you can take. Make sure you're not using a wood-based litter/bedding. these can be irritating to the skin. Use a paper-based bedding, such as CareFresh. It is recommended to bath hairless rats once a week, and to wash your own hands immediately each time before handling them. After a bath, dry your rat gently so he doesn't get chilled.
It may also help to run a humidifier or vaporizer in the room where your rat lives.
If the above measures don't help within a couple of weeks, you might want to consult a vet to make sure there isn't a fungal or bacterial skin infection. The following links will take you to directories of vets who treat small rodents. At the first site, you'll come to a log-in page. Sign in as 'member' and use 'member' as your password as well.http://www.rmca.org/Vets/index.php?action=listhttp://www.ratfanclub.org/vetref.html
If you want to try an alternative treatment as well, buy some natural Vitamin E capsules. Prick one open with a pin, and squeeze the contents onto the skin. Massage it in gently.
If you have more questions, just let me know by clicking on REPLY. I hope you'll be able to clear up your rat's skin.