I currently have Kolstein Varicores on my bass, but I recently replaced the nasaly G-string with a Pirastro Flexocor medium G-string, courtesy of TBer tnaturner.
Huge improvement in sound and feel. This string definitely matches the rest of the set well.
However, the Flexocor string tends to grab bowhair a lot more than the Varicores do. Rosining with the Kolstein Soft, my bow grabs the Varicores just right, but is a lot grabbier on the Pirastro string. Perhaps this was the intent of Kolstein when formulating the string: just right for their own rosin.
The difference in bowhair grip was somewhat distracting. So I went back to a version of my old winter rosin: a few swipes of Pops, and then a few swipes of Nymans. This time, I replaced the Pops with the Kolstein Soft.
I try this out at rehearsal on Beethoven's 4th Symphony: not very grabby and uneven along the length of bowhair (grippier towards the frog). Not good for winter playing.
So I use a couple of swipes of Kolstein Soft on top of that: Bingo! Just the right amount of grab so that the individual notes can be heard clearly. Just the right feel with the bow also. I can feel every note that I play (that is that I intend to play).
Too much of just Kolstein Soft means too much grab, which leads to a sort of crunch of notes at higher passages. Nymans during winter leads to the same problem, but with a more slippery feel.
But using a few swipes of Kolstein soft, then a few swipes of Nyman's, and finally a couple of swipes of Kolstein soft again gets just the right tone and feel for me. (maybe I can even skip the first step and use Nymans first, but I don't want to ruin a good thing.)
Kolstein Soft + Nyman's 
