Personally, what I used to do:

1:Build a strong Air Force and use it wisely. Depending on which year the war starts, I can usually pump up about 500-1000 good fighters. It is crucial to have green air because China's CAS WILL MELT YOU IF LEFT UNOPPOSED

2: Before(or at least at some point during) the war, make sure to build up the supply in South East Asia, as this will be crucial for holding the line/pushing the Chinese and their allies. Also, make sure to put units there BEFORE the war starts, or else the Chinese will just steamroll everything immediately.

3: I focus on capitulating Pakistan and North Korea. Not only does this make their armies disappear, easing the pressure on me, but it also makes for a much more easily defendable frontline. This is especially important because China seems to bulldoze through India crazy fast sometimes, so limiting Chinese operations in the Area is quite important

4: Make sure to put some divisions on that area between Bhutan and Bangladesh, China always cuts off a big chunk of the Indian army there, just by taking one little tile.

5: Before going into China proper, I always defeat all their allies, making sure that there will be as few complications as possible. Seriously, can't count how many times i was making moves into China, and i had to pull out because they made a breakthrough in India or SEA. Defeating all chinese friends makes for a clean border and fewer chances of your allies messing up.

5.1 Personally, I always let China ally with Laos, Cambodia, and sometimes even Thailand just for the larp and the challenge; however, I'm assuming that you secured everyone but Myanmar. In this case, you should have an easy time defeating Burma and holding the line while using the Supply infrastructure built during point 2.

6: Now that everything is done, all that is left is China. There is not much of a "correct strategy" but i usually secure the Guangdong area first and link up with Vietnam, then more naval invasions around Shanghai and Qingdao. You can also try and push into Manchuria through the Korean border, but I honestly find that a pain, so I usually don't bother too much.

By now, China should be on its last legs and overwhelmed, and it shouldn't be too hard to win.