The way I do it is by animating the start and pitch indeed. And use short midi notes. You’ll have to practice a bit and try different combinations to find the right sound and timing.
If you trigger a sample with pitch = 1 and then program some short notes with the pitch gliding down from +12 to +3 and a little startpoint offset and then trigger the sample with original pitch again, it will already have the effect of a transformed ‘baby scratch’. Adding pitch - 7 notes just before triggering the original pitched note will improve the effect. Just make variations on that pattern and use different start piont offsets to create more interesting patterns.
I will make a tutorial video and downloadable demo track, then you can even copy scratch patterns from my example track. I hope that I’ll have time for that soon.
For live performances I use a SenSorSuit and the skrtZz pen that we developed a while back. The skrtZz pen software might even be worthwhile to release at some point. I will discuss that with the team.