I am inclined to agree with jallenbass above and develop fast clearly articulated sounds bowing on-the-string, then semi-off before tackling spiccato. Much of Bozo's playing above is perhaps semi-off the string that still relies on the flexibility of both e bow and strings. My broad ideas about each of these bowing styles have been lifted from a previous thread started by Chapter7Seeds on July 21, 2020.
"LesFret, this is my spiel about Off-String Bowing!
The string is a spring, the bow stick is a spring, the hair is a spring. Your bow hold, wrist and arm must respect and work with these springs in all forms of bowing. If you understand these relationships then bowing becomes easy and fun.
The bow stick rotates around the R thumb (pivot point). The index finger has two tasks. It hooks over the stick to control the height of the bow point and guide the bow movement at 90 degrees to each string. Working with the thumb it hooks the bow down onto the strings in (broadly speaking) three forms of bow stroke. On the String, Off the String and Semi-Off the String.
Off-string strokes are where the bow hair is bounced into/dropped onto the string as the hand moves back and forth sideways. The flexibility of the stick, hair and string causes the bow to rebound and be trapped by the hand for the identical return stroke. The sound is often lighter than on-string bowing and has lots of character
The stick and hair are most flexible at the middle of the bow. Begin the off-string adventure here by bouncing the bow vertically with no sideways movement. Use the index finger to rotate the stick around the thumb and strike the string. The index finger will trap the rebound each time like dribbling a basketball. The point of the bow will rise and fall a lot and there will be virtually no sound. The moment the bow starts to move sideways (like a "vee" with a rounded bottom) as it drops and rebounds you will begin to make short spikey sounds. The sideways movement can come from experimenting with movements of the fingers, wrist, elbow or a combination of the three. I call this a STRUCK STROKE. It is also possible to produce a RICOCHET bowing (bouncing more than once in each direction) using this index finger/ thumb relationship.
Once you get comfortable with this form of bounce, say using 8th notes at quarter = 80 - 90, move it around the length of the bow hair. In the upper half of the bow it still rebounds well but sounds become softer and lighter. As you come back towards the balance point of the bow you will notice that the original "Vee" shape movement loses its springs. You begin to carry the bow more through its bounce in a shallow scooping motion. Until you reach the balance point the tip of the bow will probably rise and fall more that your hand. At and inside the balance point the bow stick will tend to travel parallel with itself as you carry the bounce. Inside the balance point you can use the bow weight help you GOUGE notes out of the lower strings, very useful for FF quarter notes in say Beethoven.
You can clearly hear the difference between the length of the struck and carried bounce if first you pat the back of one hand vertically with the other then brush the other hand sideways about 4" in a longer flatter shallow scooping motion. I call this my HAYDN / MOZART bounce, eg repeated 8th notes in Eine Kleine Nachtmusik, that produces warmer longer bounced sounds with more life and character than playing on the string.
As well as shortness and character of the off-string notes there are speed and dynamics to consider. On-string playing can clearly produce musical sounds of any length and dynamic if you are careful with bow length, bow weight and contact point. Off-string bowings, be they struck or scooped, tend to work well in different narrower speed ranges. Faster or slower will tend to force you back down onto the strings again, especially for louder dynamics.
My understanding is that the Italians invented the more middle-of-the-bow SPICCATO to produce clear frothy sounds, full of life Eg. Vivaldi "Four Seasons" rapid 16th notes. This can easily become a semi-off-the-string bow stroke called SAUTILLE to produce very fast chuckling sounds. Because the bass bow is heavier and slower what we tend to call Spiccato is often more like the warmer bounce closer in to the bow hold.
There is lots of experimenting to do. Each bow and player are different and some bows JUST WILL NOT produce a decent spiccato. Time to trade in for a better one? This is also why I would always upgrade my bow before I upgraded my bass (in a perfect world) and why people pay thousands."
We are still guessing whether you are using German or French bow but the broad principles of each bow stroke still apply.
Best wishes, DP