I'd say focus more on the fundamentals of an area (amenities, transport, schools, jobs etc.), than looking at specific case studies which are more speculative and opinion based, rather than factual.
When looking for a good property to flip, the two main things to consider are:
1) Will you make a profit - try to value the property as accurately as you can, by checking comparable sold prices and trying to ensure you account for all costs involved in the purchase and refurb of the property.
2) Will you be able to sell it easily - if the area has good fundamentals and you've carried out the refurb to a high standard, then you'll more than likely have a quick sale at the price you want.
In terms of specific areas of Manchester, I've recently done a refurb in Reddish which has great amenities and transport links. Denton and Droylsden are also good areas which are well connected and where you can get a bit more for your money compared to areas closer to the city centre.
But that being said, there are plenty of areas in Manchester that meet the criteria I mentioned, so you have plenty of choice.
I hope that helps,