Portrait Study #1 - Mimicking paints

I'm so eager to get on with my planned portrait project, but I keep finding new ways of improving on my previous pieces which is holding me back from actually beginning the project at all. Rather than just thinking of new techniques and workflows in my head however, i've decided to start putting those thoughts onto paper (in my case, a digital tablet) to be able to see the progression and differences throughout my portraits. What i'm really trying to figure out most however, is how to mimic oils as accurately as possible. I follow the work of this brilliant artist named Sam Spratt, he manages to get so close to the look of traditional oils that its almost as if it were actually done with paint on canvas, and that's what i'm striving for. I'm getting there slowly, but there are still a few things i'm trying to figure out. 

In this piece, study #1 , i've been focusing on different ways to use colour, trying my best not to shy away from using heavier accents and bolder tones. I tried creating a few brushes of my own in attempt to get a more acrylic paint look, and it's an improvement from the last portraits, but it still needs tinkering with. I'm just so used to my "palette knife" style brush that i'm almost too stubborn and rather reluctant to try completely new brushes. Onto the next study.