Variation 12 is an excellent exercise for developing control of the bow in the air and increased awareness of Dividing the bowstroke into fractions of the length of the bow..
In bars 8 and 9 pay attention to Ševčík’s commas, and plan when to lift the bow. Practice looping the bow pattern of bar 9 on open strings, making sure that the second note of the slur in beat 3 starts in the string but finishes out of the string.
In bars 10 and 12 and similar places, keep the sound resonant and the bow settled in the string. Practice your half-bow To begin the note the bow grips the string followed by a release during the stroke. Aim for a short sound with lots of resonance. with finger interchange (alternating fingers).
Add your own dynamic markings to bring out the phrasing structure and contours of the melody.