Rubber boa question

[serpenteye]

I am getting a rubber boa tomorrow from a guy somewhere in town. I have had these snakes before, but they seem to be really picky when it comes to cageing ect. What do you think is better...

...Natural substrate such as dirt,moss,old logs ect.
Or a much cleaner substrate such as news paper or whatever else. I know that they need a place to dig in and hide, but dirt is ...well dirty. Thanks for your time.