A thesis is technical story which you are telling the world through your expertise on fraction of knowledge in Computer Science. Quite a few of my acquaintances have gone through this experience.
I was darn lucky in my second graduate program with my professor playing a godfather.
My background is aligned with the situation you are currently facing, so maybe my answer would help you. More often than not, at good universities, Profs are more inclined towards research and less inclined towards teaching and guiding students. It would perhaps be a good idea to stop depending on your Prof for further assistance.
Having said that it would be essential to keep him/her in the loop.
Stack Exchange network consists of 175 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers. It sounds like you have two major concerns about getting quality feedback from your advisor: (1) he's busy, and (2) he's not as familiar with your new topic. To get the best feedback possible from your advisor, make sure that whatever you send him to review is as polished as possible.
I think my work is good and I will pursue trying to get it published in a journal once my actual M. is done, so I am not too uncomfortable with the things I've written.
Suddenly you realize you’ve explained something differently or too many times in different chapters, or you find some blatant contradiction that you’d never seen between chapters 2 and 5.
Then, you’ll need to wait for feedback from your advisors, which will mostly likely be infinitely useful but may not be as quick as you’d hope.
It will also help if you identify and tell him about the areas where you think you most need extra high-quality feedback: "Could you tell me what you think of the formulation in Section 3, I'm not so sure about that part." Even though your advisor is not an expert in your new topic, he's an expert in and he knows what good work looks like.
He knows when an argument seems weak and "hand-wavy" and when the evidence on offer doesn't support the claim.