Hi Cathy, thank you so much for your response and I am glad to see that my feedback helped 
I used schmincke mainly because they are super-soft pastels and stick to the surface extremely well.
For details I used some other harder brands as introduced in this thread:
Yes, the choice of pastels is super important. I remember how difficult it was to cover the surface completely while I used Faber Castell, the first brand recommended by my teacher back then.
I strongly recommend that you try shmincke. I’m sure you’ll be amazed at how easy it is to make the surface “whitedotless” with this brand. 
All the best,
Maki