I'm using counter attack all the time so I know something about KV-1.
I think there are only 2 ways to make use from KV1.
First: stack KV-1 with SU85 behind. It's really deadly combo for Tigers and Panthers.
Yet you can be countered by infantry easily.
Sceond: Garden T4, rely on ZiS (risky) and then just spam KV1s. 1 KV1 is not useful, 2 are still easily countered, but of you have 3, nothing can stop them. Garden schrecks, garden Panther. Just go forward and shoot. When one has less than 50% HP, cover it behind 2 others.
Only really massive AT attack (Pak40, raketen, schrecks, panthers) can stop 3 KV1.
when all 3 have about 50% retreat and repair.
Only threat to KV1 are Elephnat, Jadgtiger and Pak43 but that's why you have B4
It's not designed to flank like T34, it does not have good AT power like SU but 3KV ale always better (more universal, less chance to lose them) than 3 SU85s or 3 T34/76.
Altough I feel like exp needed to vet should be little lower.
It's not hard to get vet 3 with SU, Sherman, Jackson but it's really hard to get vet 3 with KV1.