Watch this tutorial to get a better idea as to how it works.
In multi-cam mode, you have to select and have one principal audio track, usually the best one. All others are turned off. This audio will be on track 2, the cut video on track 1. The audio remains constant whereas the video gets cut.
The role of multi-cam is to select cuts from one camera to another, not special effects.
Once you have finished the multi-cam part, exit it and do whatever editing that you want.
First, can you please read this post and give us the information requested there. At the very least we need to know which version of MEP you are running.
I'm not sure I understand what you mean when you write that Only one audio track will play in Multicam mode. Unless you have designated that the audio from one of the cameras is the Master, when you cut from one camera video to another you also cut from the audio of the first camera to that of the second. Are you saying you want to be able to simultaneously use/mix the audio from all the cameras? That will necessitate creating a separate mixdown of all your audio tracks. This is possible but will have to be done as a separate process, I think, and does raise the potential for audio and video to go out of sync.
Also I do not like just cuts. I want to use slow fades
This is possible but you have to create the complete timeline with all your camera cuts first. You can then change the transition between those cuts in exactly the same way as you would for non-multicam video. However, you do need to be careful because cross-fading the video will also cross-fade the audio (with the potential to "lose" a second or so at each transition), unless you deliberately unlink the audio and video tracks before creating the transitions. However, you can then lose audio/video sync because one part, the video, is effectively "shortened" whilst the audio is not.
As Jeff says, be careful when making transitions. Use the drag the front end or tail end of a clip over the adjacent one, or use the correct buttons in the Edit/Object trimmer to create and adjust the overlaps. Make sure that the clip itself does not get moved. Also, do not use the change transition length feature on a transition of the clip and those to its right will be moved. Again, you do not want to accidentally move a clip as the video will go out of sync with the audio.
Let me know if you want to see how to use the Edit trimmer to make transitions.
I used to be able to make beautiful slow transition in Premiere Pro. Since Premiere crashed (I bought the computer a few years ago the software on it and did not receive the discs) I am forced to use cheaper software. Now I have to start my edits all over from scratch. So all of you are basically telling me what I need to do can't be done with Multicam. Beside the fact that cuts will never convey the feeling of slow orchestra music.
You cannot predefine a transition and have it applied on the fly in either MEP or VPX, and you cannot simply apply a transition length to all of the objects or they will move. The way it works by default is that each object would move to the left to make an overlap with the left side object, and you don't want that. Has anyone found another way to do this?
You create the first transition by dragging the bottom left handle of the first object where you want a transition, to the left over top of the left object the approximate length that you want. Then hit N to open the Edit Trimmer. Adjust the length of the transition as shown below and the click on the right scissors button to move to the next interface. Only use the buttons indicated to increase/decrease the transition or a clip will get moved. If you don't want a transition, simply click on the scissors again to go to the next interface. As you can see, you can precisely get the length of the transition.
Note that you should do any repair work to the objects before starting, like colour correction, shot matching, audio cleaning. And you may want to do a render export, then import the cleaned file to use. Note that I have a problem in matching the colours of my two cameras, and one was more sensitive to low-light conditions.
Lastly, you can do this still in multi-cam mode or with it turned off.