A wonderful tute, Kenny. The outcome is outstanding really.
Ruin the HS? Psh, don't sell yourself short. Your work is fantastic 
I like the texture shading step you added as well. Did you leave the paint to semi dry before wiping it away? It adds a lot to the HS for me. I'll have to start doing it to mine now.
Hmm.. steady hands? You can try holding the HS against the table in one hand [or pushed into some clay] and rest your hand on the table as close to the hs as possible. It should give you some added measure of control. Your results are great though, you hardly notice any futzy edges at all.
Always do your best in everything you do, and live on, happy. - Aya