The Roto Brush and Keylight Effect

It is pretty difficult to tell from footage of your screen taken by a phone but here are my initial thoughts:

Start with a loose garbage matte then duplicate the footage at least 3 times. Pull one procedural matte from the dark areas, another from the light and you should be able to isolate the areas I highlighted including the hair and a lot of the body.

Motion stabilize the sunglasses so they do not move in the frame using Mocha AE or AE;s motion tracker on another layer then hand roto the sunglasses by overlaying a colored solid with a blend mode that lets you see the edges, then add a null, tie the null to the motion stabilized layer and parent the track matte and the footage to the null to put the movement back in the shot and add it to the track matte to cut out the parts of the sunglasses that are in front of the white wall because nothing else is going to work. Try Rotobrush on the areas like the left hand. Create another track matte for the parts of the arm and the belt that you cannot separate from the dark background any other way. 

If the footage is high quality and not more than 30 fps and I wanted about 10 seconds of this shot prepared for layering I would tell my client that the shot would take at least a day. If the footage is from a mobile device and it's only 8-bit and highly compressed I would tell the client that there are no guarantees I can make the edges look right and it might take two days to get something I would want to put my name on. If it's just for something you want to post on Facebook and close is good enough it's still going to take several hours to put you behind that dancer. 

Hi, yes it is doable. You need to roto out Person B and place that layer above the person A layer. The top layer will always  appear on top of/in front of  the lower layer.

First, trim both shots so that you are not wasting any time on frames that will never be in the final edit.

Second, do the best job you can with Keylight on the Greenscreen shot. This may require you to do a little hand roto and create some garbage mattes. The most efficient technique depends entirely on the shot.

Third, if you also need to remove the background from the second shot carefully analyze the shot to determine the most efficient approach. Just using Rotobrush is almost never the most efficient approach. If there are areas of high contrast or areas that have solid colors you can create procedural mattes for those specific areas. This requires that you create multiple copies of your footage, do some rough rotoscoping by hand to remove most of the background before you start, then use a combination of procedural mattes and Rotobrush to refine the mask. When you have all of the sections cut out you pre-compose all of the masks and use that pre-comp as a track matte on the original footage. You will go crazy and never get the shot done if the actor's whole body is in the shot and the background is complicated. For any specific suggestions I need to see your shot. A shot like this 80337703

is going to be a lot more difficult than a shot like this 311299536

But both of them are doable. 

While I'm at it, here's a little tutorial I did a few days ago showing how to create a procedural matte using high contrast footage and the black and white filter. This is just one of the techniques that I might use to generate a matte for the Fishermans arms. 

Here's a pretty good start on one of the high contrast pre-comps that would be used to isolate the fisherman from the background. 

That is just duplicates of the footage with the same settings for Black and White and a white solid as a garbage matt for the inside of the fisherman. The hair and most of his body are now 100% white so I'm well on my way in just a few minutes. 

Different techniques for the other colors in the shot and a black solid with a loose animated mask as an overlay and I should be able to completely remove the background in this shot with just a few frames of Rotobrush around his hair. Here's a composite against a blue solid so you can see the quality of the matte. Just a bunch of copies of the footage with some different procedures, and yes, with a little motion tracking and a shape layer path as an additional white source I could even include the fishing pole and line. 

Standard answer: Show us screenshots/ reference frames of your footage and people can advise. that said, you probably can't play it lazy and will need to do a lot of traditional masking. Rotobrush and keying can only do so much and of course won't create believable overlaps. Likewise, your footage may need some masssive color corrections to even integrate... In any case, show us what you have.

Mylenium