You may want to check the information below.

Here is a link that might be useful: Grafting Camellias - American Camellia Society

I was over at the propagating forum about a month ago and was so surprised to find that camellias root very easily in water! I ran out and clipped a whole bunch of 3--4" tips and plunked them in a glass of water, more than half rooted quickly, now they are in their little soil pots or directly in the ground. I was absolutely amazed at how easy this was. The plant had finished blooming about a few weeks before I did this, not sure that made any difference, didn't use rooting hormone either.
Good Luck, I was so surprised at how easy this was!
Pauline

I apologize, my last posting about rooting in water was with Gardenias NOT Camellias, Smacking my forehead!!!
Pauline

C japonica is easy to root. The new branch, just firming up, is the best for rooting. You should see the sign of callus in one month. Wait one or two months, you should see the root by loosing the growth media and raising one of the rootings very gentle and carefully with a spoon. Make sure that the media is not too wet.

The best way is actual grafting.

I would encourage you to try air layering some of the limbs, which in my opinion is the best way to get a fairly good sized plant that will put you years ahead in growth, and bloom. It is fun and easy, and its not too late for this year.

There are many ways to do this, one of which is illustrated on the link below. Those are my stubby fingers you will see in the photo. I make about 20 or 30 each year, it works like a dream.

Here is a link that might be useful: Air Layering Instructions

I just bought a camelia japonica 'rosea plena' that is still in its 5 gallon pot. Can I try to air layer with this? It is covered with buds and not sure if this would help/hinder the layering process.