I don't know of a specific tutorial, but maybe I can clear things up a bit with the definitions of masking and chroma keying!
Chroma-Keying: All chroma-keying is, is you telling the effect what colour you want to be taken out. For example, you add the chroma key effect to a clip (KH, FF, it doesn't matter) and you select the colour blue. Now, all of the blue pixels in the clip will be made transparent, so if you have a layer underneith the clip (like a different background) the background will show through where the blue pixels were taken away. The reason green-screens work best is because there is one solid green colour, and then the person. Since the green is so solid and together, it is easy to cancel out that one colour, and have the person still show through. Obviously, green-screening only works when you use real people. So chroma-keying footage like KH or FF is much more complicated, because of all the different colours within the scenes. If you can find a scene that has one large chunk of colour (like a blue sky) then it is a little easier to get rid of that chunk. Either way, chroma-keying is far from perfect, and I never reccomend using it for footage without a green-screen. Some people "mask" with it, but that cannot be truly called "masking" because "masking" means something else.
Masking: Masking is a process by which you draw an outline via a series of points called anchors around a person in a scene. You are essentially cutting this person out of their background. Masking is a much cleaner and more efficiant way to take someone (or something) and place it somewhere new. It is a lot of work, and takes a lot of patience and practise to get it looking believable, but that is what I reccomend when you cannot chroma-key. Masking allows for fine-tuning and more precise cut-outs of the person or thing.
I hope this helps...Im sure you knew what the terms meant, but yah...xD Ill just be quiet now. Let me know if I completely misunderstood you, and I will try to find a tutorial for you on what you are looking for.