Later!
I like to think of three sizes of shift. Small, when your hand moves a tone or less, either on the same finger or from finger to finger, eg A (1) - C (4) on G string. Medium or Walking, where your index finger passes your second or fourth fingers, eg A (1) B (4) C sharp (2) D (4). Leap of faith (or bungee jump) eg B flat in 1/2 position to B flat in thumb position.
I apologise for being so long-winded with the above (which you might already know) but the review sets up what follows, a technique of shifting.
Try this idea. Hold the bow stick vertically, point up, between your index finger and thumb at the frog. Release just enough pressure and the stick slips. Nip between finger and thumb to stop it slipping. This release-nip can happen a number of times in the bow length. You can liken it to the way the callipers of car disc brakes work.
Shifting shouldn't feel like you are tearing the ends off your fingers. I release the string just enough to take the brakes off as I start to shift. While I'm shifting I hold the string almost to the fingerboard. I then use this relaxed nipping action to end the shift after dropping in my next finger at a shallow angle. You get calluses from doing this and the calluses help you to shift freely anyway! By the way, the bass neck should be slippery-smooth and never gloss varnished, for ease of movement. If your fingertips are too dry just touch them to your temple - there is a little bit of oil there.
Yes, keep your hand in good shape, ready to play any note in the new position. Beware shifting up 4 - 4 if possible because the 4th finger has very little sideways strength and the fingers lose correct spacings. I try to shift from one finger to another, two notes per position where practical, allowing for bowings and string crossings.
The next part is to get your hand from point A to point B without jerking. I like to use a stabbing motion that rotates the upper arm in the shoulder, like stabbing the kitchen bench with a carving knife. This is quicker, lighter and less cumbersome than dropping or raising the whole arm from the shoulder (like a chicken flapping its wings).
If I leave my elbow at the same height and shift any distance my hand will pull into the fingerboard and jam on the brakes, perhaps prematurely, because the hand moves in an arc around the elbow. If the elbow moves slightly in the direction of the shift before the hand takes off then two things happen. The first is that the arc is flattened out by moving the centre of the circle (the elbow). This helps to take the brakes off, move the hand freely then nip them on again. The second is that the hand plays catch-up then passes the elbow in a springboard effect, enabling you to make a quick darting movement along strings without jerking. Suddenly shifting is relaxed and effortless.
After all the above blah blah I would suggest the following :-
(1) Review your present shifting technique to make sure it is as good and reliable as possible. Adapt any or adopt all of the above if you like. Maybe your ideas are better!
(2) Review your note/position finding techniques. Try the idea of muscle-memory. Invent lots of little challenges to perfect.
(3) Review your concept of beautifully in tune scales, major and minor, and their arpeggios. Hear and practice scales slowly and deliberately as two groups of four notes with a pause between. Practice scales in thirds and other intervals. Try to pre-hear notes and move directly to them with confidence. Practice Gary Karr's "vomit" exercises up and down strings, eg A flat to B flat, A flat to C, etc, up the A flat scale on the G string, using first finger on A flat and choosing 1, 2 or 4 to land on the upper note. Again, invent your own challenges.
(4) Build confidence in your ability to pre-hear notes and move directly to them. Nobody plays perfectly in tune all the time. The best players are very good at quickly correcting themselves. The acoustics of the bass are in our favour. We can correct before the vibrations fully get going.
(5) Look out for two small publications. The first is Abe Luboff's "Sevcik for Bass". He asks you to repeat the theme of a set of variations with a very definite set of instructions about shifting. The second is "Technical Studies for Double Bass" by Jiri
Pichlik, published by Feja, Berlin. It works through all possible fingering patterns when crossing strings while also working up and down strings in half tone steps and is good for building technique, confidence and stamina.
The above advice is very long-winded but I hope it helps!
DP