Suppose you are interested in the thought of a famous historical figure in philosophy. Devoting yourself to the study of this figure, you realize that you need to publish work on that philosopher. Unfortunately, the number of philosophers who have written about your figure over the years is so great that nothing novel, interesting and rationally supportable can be said about that philosopher's work. Indeed, the ratio of philosophers writing about famous figures to the writings that are actually worth reading is thousands to one. But fear not, you can still have a successful career as a historian of philosophy. All you have to do is follow my simple plan.
Find some interpretation, any interpretation, of your philosopher's work that no one has given before or at least one that, due to its manifest irrationality, few philosophers would long consider. Basically, get drunk or drop some acid, spin in circles like a kid, then compare some random passages from unrelated works and see if they might have some tangential relation to each other. This may be difficult since it's potentially creative. But don't worry, you can simply misread a sentence or free associate from the text. Once you've got an interpretation, no matter how conceived, to start from, you can proceed to defend it.
For example, suppose you run across a passage in Descartes that you could interpret as indicating that Descartes is not a dualist. So, in the Sixth Meditation when he calls the human mind a body a union or unity, then you've got a case for his being a monist. Remember the passages you choose do not have to clearly indicate your preferred interpretation. All you need is that the passage be interpretable in some tendentious way as supporting your claim.
You know, of course, that Descartes repeatedly states his intention to argue for dualism, and he in fact presents several arguments throughout his work for that conclusion. But, this is key, his explicit stated belief is not a reason to give up on your interpretation. Instead, refer to Descartes' explicit belief as the "standard" or "traditional interpretation". Or, better yet, you can use a slightly pejorative term, such as the "common view" or the "conventional wisdom".
You're claiming that Descartes is not a dualist. And you have a couple of passages that, if you squint really hard, might suggest that he is not a dualist or had some misgivings about his argument for it, but what do you do about all those passages in which he explicitly states that his goal is to argue for dualism and all those places in which he argues for it?
First, never refer to the passages that clearly indicate Descartes' view. Just pretend they don't exist. Second, if forced, you can say, "I still haven't worked out all the implications for all of Descartes' works. I would need to look at that in more detail." Third, if interlocutors insist on an explanation of the relevant passages, throw out all the red herrings you can. "What is a real distinction after all? What does Descartes mean by 'real'? What is it for these to be distinct?" If you cast enough mud, you can make it impossible to see.
In short, take a view that no rational reader of your philosopher could have on any informed reading, support it with tangentially-related texts with little bearing on the question (after all, that's the only way you'll undermine the philosopher's explicitly stated view on that topic) that you can interpret tendentiously to support your view, ignore all the passages in which your philosophy explicitly denies your interpretation, and, when forced, deny the obvious interpretation of these passages or at least try to cast doubt on them. Now you are well on your way to being a professional history of philosophy scholar. Remember that you need to say something that has not been said before, so say anything and try to make it stick. Nobody cares whether you are right or even reasonably supported or supportable. All you need is something novel, and the more blatantly your interpretation conflicts with the text, the more novel your view is.