Newbie - Building File Cabinet Smoker

I have done a lot of reading on the forum on people's File Cabinet builds, and I have learned a lot and have some ideas on what to do, but I have a couple of questions.  Well, that is a lie, I am sure I have more that a couple, but a couple to start with.

I did a burn last weekend in the cabinet, I built a fire in the bottom and second drawer.  The top drawer would burn to much, it kept going out when I closed it do to the updraft.  My question is how many burns should I do and how careful do I have to be with the paint on the inside?  If I do another burn, should that be good enough?  The first one was for about an hour.  Do I have to do any scraping with sand paper or a grinder?  

Also, do I have to season the inside?  I guy at work is building a smoker (for a tank) and said it should be seasoned.  Is that just putting oil on all sides of the drawers and the inside of the cabinet?

Any other insights are welcomed.