TECHNIQUE
What is the best way to improvise a barre cord when you can't make the
chord?
You can play parts of the chord that are easier to
finger depending on what's required.
If you need a low, grounded or rooted sound
concentrate on the lower-pitched parts of the
chord.
If you need higher sounds, release some of the
bass notes and find the pitches that get the job
done for you.
What's a better approach to play linear (up & down the neck) instead of
getting caught on the 5th fret, for example?
A good jazz approach to this is to begin with your chord tones and play
them up and back down each string.
A good order for this might be Major Seventh, Seventh, Minor Seventh,
Minor Seven Flat Five, Diminished Seven, and then the other six types.
Do the same thing with your scales, starting with Major, then Harmonic
Minor, then Jazz Minor, then other scales you think you might use.
I recommend the Cycle of Fifths (C, F, Bb, Eb, Ab, Db, F#, B, E, A, D, G)
as an order for moving through the keys.
Do you recommend performing improv with a guitar pick or without?
The decision to use a pick is a very personal one based on what kind of
sound you want and how you like to play. The goal of American Music is to
sound like you, so each decision you make about your sound should be
personal and pleasing to you.