There are as many ways to transition cats from commercial to raw as there are cats.
Some cats will take to raw immediately and not even need any transition time. (My own cats did this... their very first raw meal was half-frozen chicken breast and they were so doggone excited about it that they were ripping pieces off faster than I could cut. *chuckle*)
Take the transition just as slow as your kitty desires, but don't make him go hungry. Put some of the raw on a plate right next to his regular food while he's eating for several days. Just enough so he can smell it while he's eating and begin to associate the two together.
Then drop just a bit of his regular food on top of the raw and offer that before his regular food for several days to see if he'll try it. If not, offer the regular food next to the plate of raw for a few more days and then try again.
You could also sprinkle freeze-dried meat treats on the wet food. Stella and Chewy's makes some, as does Whole Life and many others. Cats often find these treats irresistible and they sorta melt into the wet food, so they can't easily be picked out.
Other things that might tempt your furbaby to eat the raw are: Parmesan cheese, the juice from cans of water-packed, no-salt-added tuna and sardines, catnip, and strangely enough, flaked fish food.
Here are some links to articles on transitioning tips and tricks: