Another factor in your issues is that wicked doesnt have the erasing capabilities as other lines such as Etac Efx, Createx illustration and a few others. Erasing is kind of like a system that you put together with types of erasers for certain things, substrate, and paint that conforms to your painting style. Erasing is a whole different animal in itself. Ive found being able to layer your erasing as well will help create certain textures and highlights in the process of your painting.
Ive found that using posterboard is my ticket for how i paint with erasing, and using Etac Efx with fabercastell pencil erasers. The posterboard has a sort of laminated side to it so it doesnt soak up the paint and it erases pretty well. Its cheap and you can get big sheets and cut them down for more. Just my 2 cents. Just speaking from my experience and hope this helps sparks some thoughts!