Charlie is a thousand times better at improvising on the trumpet than I am. And he is a natural gifted teacher. He's the man to follow (in this and other YouTube tutorials that he has generously given to the world).
To see the video
And another super little video that gives you some idea about how the trumpet, trombone and clarinet go about collectively improvising is this one:
CLICK HERE TO VIEW.
As for me, I took up trying to play traditional jazz too late in life. I had no Charlie Porter to advise me and my learning processes were more pedestrian.
A wise old friend and jazz musician - Bill Stevens, who alas died several years ago - got me started by telling me there were two ways to improvise when playing jazz. He said you can improvise either on the melody or on the chords. Bill said that if you improvise on the melody, you will sometimes sound terrible but you will also achieve some exciting things. If you improvise on the chords, he said, you will always sound 'right' but will not be so exciting.
Bill Stevens' 'chord' method of improvising over a complete tune involves doing this kind of thing with all the bars. The great majority of 'standards' (such as All of Me) comprise 32 bars, which you come to feel as four eights. There is usually some repetition of chord patterns within the tune, so this helps.